[clang] [coverage] fix crash in code coverage and `if constexpr` with `ExprWithCleanups` (PR #80292)

[via cfe-commits]

cor3ntin wrote:

> Changes LGTM, but please add a release note to `clang/docs/ReleaseNotes.rst` so users know about the fix.
> 
> Thank you for the fix!

FYI this is a regression in 18 affecting users so we should backport 

https://github.com/llvm/llvm-project/pull/80292