[clang] [LifetimeSafety] Warn on meaningless [[clang::lifetimebound]] parameters (PR #201101)

[Gábor Horváth via cfe-commits]

https://github.com/Xazax-hun commented:

We start to have some diagnostics that do not require running the actual lifetime analysis. But I suspect even if only those diagnostics are enabled we would still run the whole analysis.

I wonder if at some point we should factor this out that only the diagnostics that actually require dataflow will trigger the dataflow. 

Overall, the direction looks good to me but did some nitpicking inline. 

https://github.com/llvm/llvm-project/pull/201101