[libc++][doc] Updates the release notes.

[Mordante]

Summary

This is a preparation for the upcoming LLVM 17 release.

[jloser]

LGTM, but I haven't been following as closely this release, so there may be other things I didn't notice in the updated release notes.

[ldionne]

Nice, thanks!

libcxx/docs/ReleaseNotes.rst

46

75

Maybe add a link to the review?

[Mordante]

Thanks for all reviews!

In D141304#4037155, @jloser wrote:

LGTM, but I haven't been following as closely this release, so there may be other things I didn't notice in the updated release notes.

I also can't recall everything, I just looked at all commits in the libcxx directory during the last six months ;-)

libcxx/docs/ReleaseNotes.rst

46

That fails to build, I moved change it to `views` instead.

libcxx/docs/ReleaseNotes.rst

 Note that if you are reading this file from a Git checkout or the
 main Libc++ web page, this document applies to the *next* release, not
 the current one. To see the release notes for a specific release, please
 see the `releases page <https://llvm.org/releases/>`_.
 
 What's New in Libc++ 16.0.0?
 ============================
 
+The main focus of the libc++ team has been to implement new C++20 and C++23
+features.
+
+The C++20 format library has improved but it not yet considered stable. The
+main improvements are additional formatters for the chrono calendar types. Work
+on formatting ranges has started.
+
+The C++20 ranges library has been completed and is no longer experimental. Some
+``view`` s  have not been implemented yet. Work on C++23 ranges has started.
+
+The C++20 spaceship operator has been added to more types, the work is still
+ongoing.
+
 Implemented Papers
 ------------------
 - P2499R0 - ``string_view`` range constructor should be ``explicit``
 - P2417R2 - A more constexpr bitset
 - P2445R1 - ``std::forward_like``
 - P2273R3 - Making ``std::unique_ptr`` constexpr
 - P0591R4 - Utility functions to implement uses-allocator construction
 - P2291R3 - Add Constexpr Modifiers to Functions ``to_chars`` and
   ``from_chars`` for Integral Types in ``<charconv>`` Header
 - P0220R1 - Adopt Library Fundamentals V1 TS Components for C++17
 - P0482R6 - char8_t: A type for UTF-8 characters and strings
 - P2438R2 - ``std::string::substr() &&``
 - P0600R1 - ``nodiscard`` in the library
 - P0339R6 - ``polymorphic_allocator<>`` as a vocabulary type
 - P1169R4 - ``static operator()``
 - P0415R1 - ``constexpr`` for ``std::complex``
+- P0323R12 - ``std::expected``
 
 Improvements and New Features
 -----------------------------
 - Declarations of ``std::c8rtomb()`` and ``std::mbrtoc8()`` from P0482R6 are
   now provided when implementations in the global namespace are provided by
   the C library.
 - Implemented ``<memory_resource>`` header from C++17
+- Improved the performance of std::sort
 
 Deprecations and Removals
 -------------------------
 - ``unary_function`` and ``binary_function`` are no longer provided in C++17 and newer Standard modes.
   They can be re-enabled with ``_LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION``.
 
 - Several incidental transitive includes have been removed from libc++. Those
   includes are removed based on the language version used. Incidental transitive
   inclusions of the following headers have been removed:
 
-  - C++11, C++14, and C++17: ``chrono``
-  - C++20: ``chrono``
+  - C++11, C++14, C++17, and C++20: ``chrono``
   - C++2b: ``algorithm``, ``array``, ``atomic``, ``bit``, ``chrono``,
     ``climits``, ``cmath``, ``compare``, ``concepts``, ``cstdarg``, ``cstddef``,
     ``cstdint``, ``cstdlib``, ``cstring``, ``ctime``, ``exception``,
     ``functional``, ``initializer_list``, ``iosfwd``, ``iterator``, ``limits``,
     ``memory``, ``new``, ``numeric``, ``optional``, ``ratio``, ``stdexcept``,
     ``string``, ``tuple``, ``type_traits``, ``typeinfo``, ``unordered_map``,
     ``utility``, ``variant``, ``vector``.
 
   Users can also remove all incidental transitive includes by defining
   ``_LIBCPP_REMOVE_TRANSITIVE_INCLUDES`` regardless of the language version
   in use. Note that in the future, libc++ reserves the right to remove
   incidental transitive includes more aggressively, in particular regardless
   of the language version in use.
 
-- The legacy testing system for libc++, libc++abi and libunwind has been removed.
+- The legacy testing system for libc++, libc++abi, and libunwind has been removed.
   All known clients have been migrated to the new configuration system, but please
   reach out to the libc++ developers if you find something missing in the new
   configuration system.
 
 - The functions ``to_chars`` and ``from_chars`` for integral types are
   available starting with C++17. Libc++ offered these functions in C++11 and
   C++14 as an undocumented extension. This extension makes it hard to implement
   the C++23 paper that makes these functions ``constexpr``, therefore the

libcxx/docs/Status/Cxx20Papers.csv

 "`P0980R1 <https://wg21.link/P0980R1>`__","LWG","Making std::string constexpr","Cologne","|Complete|","15.0"
 "`P1004R2 <https://wg21.link/P1004R2>`__","LWG","Making std::vector constexpr","Cologne","|Complete|","15.0"
 "`P1035R7 <https://wg21.link/P1035R7>`__","LWG","Input Range Adaptors (mostly implemented, TODO: elements_view)","Cologne","|In Progress|","","|ranges|"
 "`P1065R2 <https://wg21.link/P1065R2>`__","LWG","Constexpr INVOKE","Cologne","|Complete|","12.0"
 "`P1135R6 <https://wg21.link/P1135R6>`__","LWG","The C++20 Synchronization Library","Cologne","|Complete|","11.0"
 "`P1207R4 <https://wg21.link/P1207R4>`__","LWG","Movability of Single-pass Iterators","Cologne","|Complete|","15.0","|ranges|"
 "`P1208R6 <https://wg21.link/P1208R6>`__","LWG","Adopt source_location for C++20","Cologne","",""
 "`P1355R2 <https://wg21.link/P1355R2>`__","LWG","Exposing a narrow contract for ceil2","Cologne","|Complete|","9.0"
-"`P1361R2 <https://wg21.link/P1361R2>`__","LWG","Integration of chrono with text formatting","Cologne","|In Progress|",""
+"`P1361R2 <https://wg21.link/P1361R2>`__","LWG","Integration of chrono with text formatting","Cologne","|Partial|",""
 "`P1423R3 <https://wg21.link/P1423R3>`__","LWG","char8_t backward compatibility remediation","Cologne","|Complete|","15.0"
 "`P1424R1 <https://wg21.link/P1424R1>`__","LWG","'constexpr' feature macro concerns","Cologne","Superseded by `P1902 <https://wg21.link/P1902>`__",""
 "`P1466R3 <https://wg21.link/P1466R3>`__","LWG","Miscellaneous minor fixes for chrono","Cologne","",""
 "`P1474R1 <https://wg21.link/P1474R1>`__","LWG","Helpful pointers for ContiguousIterator","Cologne","|Complete|","15.0","|ranges|"
 "`P1502R1 <https://wg21.link/P1502R1>`__","LWG","Standard library header units for C++20","Cologne","",""
 "`P1522R1 <https://wg21.link/P1522R1>`__","LWG","Iterator Difference Type and Integer Overflow","Cologne","|Complete|","15.0","|ranges|"
 "`P1523R1 <https://wg21.link/P1523R1>`__","LWG","Views and Size Types","Cologne","|Complete|","15.0","|ranges|"
 "`P1612R1 <https://wg21.link/P1612R1>`__","LWG","Relocate Endian's Specification","Cologne","|Complete|","10.0"

libcxx/docs/Status/Cxx2bPapers.csv

 "`P2508R1 <https://wg21.link/P2508R1>`__","LWG","Exposing ``std::basic-format-string``","July 2022","|Complete|","15.0"
 "`P2513R4 <https://wg21.link/P2513R4>`__","LWG","``char8_t`` Compatibility and Portability Fixes","July 2022","",""
 "`P2517R1 <https://wg21.link/P2517R1>`__","LWG","Add a conditional ``noexcept`` specification to ``std::apply``","July 2022","",""
 "`P2520R0 <https://wg21.link/P2520R0>`__","LWG","``move_iterator`` should be a random access iterator","July 2022","","","|ranges|"
 "`P2540R1 <https://wg21.link/P2540R1>`__","LWG","Empty Product for certain Views","July 2022","","","|ranges|"
 "`P2549R1 <https://wg21.link/P2549R1>`__","LWG","``std::unexpected`` should have ``error()`` as member accessor","July 2022","|Complete|","16.0"
 "`P2553R1 <https://wg21.link/P2553R1>`__","LWG","Make ``mdspan`` ``size_type`` controllable","July 2022","",""
 "`P2554R0 <https://wg21.link/P2554R0>`__","LWG","C-Array Interoperability of MDSpan","July 2022","",""
-"`P2585R0 <https://wg21.link/P2585R0>`__","LWG","Improving default container formatting","July 2022","",""
+"`P2585R0 <https://wg21.link/P2585R0>`__","LWG","Improving default container formatting","July 2022","|Partial|",""
 "`P2590R2 <https://wg21.link/P2590R2>`__","LWG","Explicit lifetime management","July 2022","",""
 "`P2599R2 <https://wg21.link/P2599R2>`__","LWG","``mdspan::size_type`` should be ``index_type``","July 2022","",""
 "`P2604R0 <https://wg21.link/P2604R0>`__","LWG","mdspan: rename pointer and contiguous","July 2022","",""
 "`P2613R1 <https://wg21.link/P2613R1>`__","LWG","Add the missing ``empty`` to ``mdspan``","July 2022","",""
 "","","","","",""
 "`P1202R5 <https://wg21.link/P1202R5>`__","LWG", "Asymmetric Fences", "November 2022","","","|concurrency TS|"
 "`P1264R2 <https://wg21.link/P1264R2>`__","LWG", "Revising the wording of ``stream`` input operations", "November 2022","|Complete|","9.0",""
 "`P1478R8 <https://wg21.link/P1478R8>`__","LWG", "``Byte-wise`` ``atomic`` ``memcpy``", "November 2022","","","|concurrency TS|"
 "`P2167R3 <https://wg21.link/P2167R3>`__","LWG", "Improved Proposed Wording for LWG 2114", "November 2022","","",""
 "`P2396R1 <https://wg21.link/P2396R1>`__","LWG", "Concurrency TS 2 fixes ", "November 2022","","","|concurrency TS|"
 "`P2505R5 <https://wg21.link/P2505R5>`__","LWG", "Monadic Functions for ``std::expected``", "November 2022","","",""
 "`P2539R4 <https://wg21.link/P2539R4>`__","LWG", "Should the output of ``std::print`` to a terminal be synchronized with the underlying stream?", "November 2022","","","|format|"
 "`P2602R2 <https://wg21.link/P2602R2>`__","LWG", "Poison Pills are Too Toxic", "November 2022","","","|ranges|"
 "`P2708R1 <https://wg21.link/P2708R1>`__","LWG", "No Further Fundamentals TSes", "November 2022","|Nothing to do|","",""
 "","","","","",""