[clang] Respect the [[clang::unsafe_buffer_usage]] attribute for field and constructor initializers (PR #91991)

[Ziqing Luo via cfe-commits]

https://github.com/ziqingluo-90 approved this pull request.

LGTM!  Thank you @danakj for the continuous effort!

https://github.com/llvm/llvm-project/pull/91991