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

[Marco Elver via cfe-commits]

melver wrote:

A bit of archeology revealed that the feature itself has been stable for a long time, but the beta flag was used to control rollout in the target codebase at Google. I think this is just some technical debt and the beta flag should have been dropped years ago - so in all fairness, let's merge this now - if there are issues, let's try to see them early and revert if needed.


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