[clang] [clang-tools-extra] [libcxx] Reland "[clang] Enable sized deallocation by default in C++14 onwards" (PR #90373)

[Louis Dionne via cfe-commits]

https://github.com/ldionne approved this pull request.

Let's try this again. Thanks for your perseverance, this is obviously not easy to land but it's important to get it done. Let's hope everything has been addressed this time around.

https://github.com/llvm/llvm-project/pull/90373