[clang] [clang-tools-extra] [libcxx] [clang] Enable sized deallocation by default in C++14 onwards (PR #83774)

[Mark de Wever via cfe-commits]

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

I have only reviewed the libc++ changes and they LGTM.

https://github.com/llvm/llvm-project/pull/83774