[clang] [LifetimeSafety] Add language option for experimental lifetime safety (PR #149592)

[Utkarsh Saxena via cfe-commits]

usx95 wrote:

>This patch and fix improved things and I see less build failures, but my problems haven't gone away.
Now Clang hangs compiling some files, it doesn't terminate.

This analysis would not be triggered with `-Weverything` anymore and would not have any side effects. So must be some other culprit as mentioned.

https://github.com/llvm/llvm-project/pull/149592