[NFC][libc++][tests] stringstream.assign should not be a subdirectory of stringstream.cons

[pfusik]

Now I think this should be rather: https://reviews.llvm.org/D151884

libcxx/test/std/input.output/string.streams/stringstream.assign/member_swap.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // <sstream>
 
 // template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
 // class basic_stringstream
 
 // void swap(basic_stringstream& rhs);
 
 #include <sstream>
 #include <cassert>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
     {
         std::stringstream ss0(" 123 456 ");
         std::stringstream ss;
         ss.swap(ss0);
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == " 123 456 ");
         int i = 0;
         ss >> i;
         assert(i == 123);
         ss >> i;
         assert(i == 456);
         ss << i << ' ' << 123;
         assert(ss.str() == "456 1236 ");
         ss0 << i << ' ' << 123;
         assert(ss0.str() == "456 123");
     }
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
     {
         std::wstringstream ss0(L" 123 456 ");
         std::wstringstream ss;
         ss.swap(ss0);
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == L" 123 456 ");
         int i = 0;
         ss >> i;
         assert(i == 123);
         ss >> i;
         assert(i == 456);
         ss << i << ' ' << 123;
         assert(ss.str() == L"456 1236 ");
         ss0 << i << ' ' << 123;
         assert(ss0.str() == L"456 123");
     }
 #endif // TEST_HAS_NO_WIDE_CHARACTERS
 
   return 0;
 }

libcxx/test/std/input.output/string.streams/stringstream.assign/move.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // <sstream>
 
 // template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
 // class basic_stringstream
 
 // basic_stringstream& operator=(basic_stringstream&& rhs);
 
 #include <sstream>
 #include <cassert>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
     {
         std::stringstream ss0(" 123 456 ");
         std::stringstream ss;
         ss = std::move(ss0);
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == " 123 456 ");
         int i = 0;
         ss >> i;
         assert(i == 123);
         ss >> i;
         assert(i == 456);
         ss << i << ' ' << 123;
         assert(ss.str() == "456 1236 ");
     }
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
     {
         std::wstringstream ss0(L" 123 456 ");
         std::wstringstream ss;
         ss = std::move(ss0);
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == L" 123 456 ");
         int i = 0;
         ss >> i;
         assert(i == 123);
         ss >> i;
         assert(i == 456);
         ss << i << ' ' << 123;
         assert(ss.str() == L"456 1236 ");
     }
 #endif
 
   return 0;
 }

libcxx/test/std/input.output/string.streams/stringstream.assign/nonmember_swap.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // <sstream>
 
 // template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
 // class basic_stringstream
 
 // template <class charT, class traits, class Allocator>
 //   void
 //   swap(basic_stringstream<charT, traits, Allocator>& x,
 //        basic_stringstream<charT, traits, Allocator>& y);
 
 #include <sstream>
 #include <cassert>
 
 #include "test_macros.h"
 
 int main(int, char**)
 {
     {
         std::stringstream ss0(" 123 456 ");
         std::stringstream ss;
         swap(ss, ss0);
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == " 123 456 ");
         int i = 0;
         ss >> i;
         assert(i == 123);
         ss >> i;
         assert(i == 456);
         ss << i << ' ' << 123;
         assert(ss.str() == "456 1236 ");
         ss0 << i << ' ' << 123;
         assert(ss0.str() == "456 123");
     }
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
     {
         std::wstringstream ss0(L" 123 456 ");
         std::wstringstream ss;
         swap(ss, ss0);
         assert(ss.rdbuf() != 0);
         assert(ss.good());
         assert(ss.str() == L" 123 456 ");
         int i = 0;
         ss >> i;
         assert(i == 123);
         ss >> i;
         assert(i == 456);
         ss << i << ' ' << 123;
         assert(ss.str() == L"456 1236 ");
         ss0 << i << ' ' << 123;
         assert(ss0.str() == L"456 123");
     }
 #endif
 
   return 0;
 }