[clang] [analyzer] Introduce the check::BlockEntrance checker callback (PR #140924)

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat commented:

@steakhal Thanks for the updates, I'm completely satisfied with them.

I don't see any connection between this commit and the buildbot failures :thinking: ... they are probably unrelated.

https://github.com/llvm/llvm-project/pull/140924