[libc++][ranges][NFC] Update Ranges status and release notes.

[Mordante]

LGTM, thanks!

Please coordinate with @huixie90 due to the merge conflicts with D142494. Can you make sure both patches are backported to the release branch?

libcxx/docs/ReleaseNotes.rst

47

Please verify whether I suggested the proper syntax.

[var-const]

I'm going to abandon this revision in favor of D142494 and D142520. Sorry about the confusion. The end result will look similar to this revision (for the release notes).

libcxx/docs/ReleaseNotes.rst

 
 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.
+main improvements are implementing formatting for ranges and additional
+formatters for the chrono calendar types.
 
-The C++20 ranges library has been completed and is no longer experimental. Some
-``views`` have not been implemented yet. Work on C++23 ranges has started.
+The C++20 ranges library has been completed and is no longer experimental (with
+the exception of `join_view` that is about to undergo an ABI-breaking change due
+to D2770R0). 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

libcxx/docs/Status/RangesMajorFeatures.csv

 Standard,Name,Assignee,CL,Status
 C++23,`ranges::to <https://wg21.link/P1206R7>`_,Unassigned,No patch yet,Not started
 C++23,`Pipe support for user-defined range adaptors <https://wg21.link/P2387R3>`_,Unassigned,No patch yet,Not started
-C++23,`Formatting Ranges <https://wg21.link/P2286R8>`_,Mark de Wever,Various,Complete
+C++23,`Formatting Ranges <https://wg21.link/P2286R8>`_,Mark de Wever,Various,✅

libcxx/docs/Status/RangesViews.csv

 Standard,View,Assignee,CL,Status
 C++20,`empty <https://wg21.link/P0896R4>`_,Zoe Carver,`D103208 <https://llvm.org/D103208>`_,✅
 C++20,`single <https://wg21.link/P0896R4>`_,Zoe Carver,`D106840 <https://llvm.org/D106840>`_,✅
 C++20,`iota (view) <https://wg21.link/P0896R4>`_,Zoe Carver,`D107396 <https://llvm.org/D107396>`_,✅
 C++20,`all <https://wg21.link/P0896R4>`_,Zoe Carver,`D102028 <https://llvm.org/D102028>`_,✅
 C++20,`ref_view <https://wg21.link/P0896R4>`_,Zoe Carver,`D102020 <https://llvm.org/D102020>`_,✅
 C++20,`owning_view <https://wg21.link/P0896R4>`_,Arthur O'Dwyer,`D116894 <https://llvm.org/D116894>`_,✅
 C++20,`filter <https://wg21.link/P0896R4>`_,Louis Dionne,`D109086 <https://llvm.org/D109086>`_,✅
 C++20,`transform <https://wg21.link/P0896R4>`_,Zoe Carver,`D103056 <https://llvm.org/D103056>`_,✅
 C++20,`take <https://wg21.link/P0896R4>`_,Zoe Carver,`D106507 <https://llvm.org/D106507>`_,✅
 C++20,`take_while <https://wg21.link/P1035R7>`_,Hui Xie,`D134952 <https://llvm.org/D134952>`_,✅
 C++20,`drop <https://wg21.link/P1035R7>`_,Zoe Carver,`D102037 <https://llvm.org/D102037>`_,✅
 C++20,`drop_while <https://wg21.link/P1035R7>`_,Hui Xie,`D135460 <https://llvm.org/D135460>`_,✅
 C++20,`join <https://wg21.link/P0896R4>`_,Zoe Carver,`D107671 <https://llvm.org/D107671>`_,✅
-C++20,`split <https://wg21.link/P2210R2>`_,Unassigned,No patch yet,Not started
+C++20,`split <https://wg21.link/P2210R2>`_,Hui Xie,`D142063 <https://llvm.org/D142063>`_,✅
 C++20,`lazy_split <https://wg21.link/P0896R4>`_,Zoe Carver and Konstantin Varlamov,`D107500 <https://llvm.org/D107500>`_,✅
 C++20,`counted <https://wg21.link/P0896R4>`_,Zoe Carver,`D106923 <https://llvm.org/D106923>`_,✅
 C++20,`common <https://wg21.link/P0896R4>`_,Zoe Carver,`D105753 <https://llvm.org/D105753>`_,✅
 C++20,`reverse <https://wg21.link/P0896R4>`_,Zoe Carver,`D107096 <https://llvm.org/D107096>`_,✅
 C++20,`elements / keys / values <https://wg21.link/P1035R7>`_,Hui Xie,`D136268 <https://llvm.org/D136268>`_,✅
 C++20,`istream <https://wg21.link/P1035R7>`_,Hui Xie,`D133317 <https://llvm.org/D133317>`_,✅
 ,,,,
 ,,,,