[clang] [clang][ThreadSafety] Check trylock function success and return types (PR #95290)

[Dan McArdle via cfe-commits]

dmcardle wrote:

> LGTM -- that new documentation is fantastic, thank you for that!

Thank you! I hope it saves future readers some time.

I don't have write access, so feel free to merge unless we're waiting for @aaronpuchert to review :)


https://github.com/llvm/llvm-project/pull/95290