[clang] [LifetimeSafety] Warn on incorrectly placed `[[clang::lifetimebound]]` attributes (PR #196144)

[Gábor Horváth via cfe-commits]

Xazax-hun wrote:

Nit about writing PR descriptions:
* You do not need to say "In this PR", just say what the PR does. It is evident from the context.
* No need to explicitly call out that you added tests. That is the basic bar that we have for all contributions. We usually only call out of there is a reason why we cannot add a test.

https://github.com/llvm/llvm-project/pull/196144