[libcxx] Add deprecation notices to macros deprecated in P0883R2

When P0883R2 was initially implemented in D103769 #pragma clang deprecated didn't exist yet.
We also forgot to cleanup usages in libc++ itself.

This takes care of both.

Differential Revision: https://reviews.llvm.org/D115995

NOKEYCHECK=True
GitOrigin-RevId: 4e730aeb731cb9b7116ed51bbef662d363f72b66
10 files changed