[clang] Thread Safety Analysis: Graduate ACQUIRED_BEFORE() and ACQUIRED_AFTER() from beta features (PR #152853)

[Marco Elver via cfe-commits]

melver wrote:

Thanks! Intending to merge this one by end of week.

FWIW, I want to commit this before https://github.com/llvm/llvm-project/pull/142955 - which uses `-Wthread-safety-beta` to guard the new features.

https://github.com/llvm/llvm-project/pull/152853