[clang] Thread Safety Analysis: Don't warn at joins that re-branch on a try-lock result (PR #209796)

[Marco Elver via cfe-commits]

melver wrote:

Note, to get this in for Clang 23, we need to merge soon - Clang 23-rc1 has been cut end of last week. We need to propose this as a cherry-pick bug fix once landed and soaked for a few days.

https://github.com/llvm/llvm-project/pull/209796