[llvm] Reland [BasicBlockUtils] Handle funclets when detaching EH pad blocks (PR #159379)

[Gábor Spaits via llvm-commits]

spaits wrote:

@rnk I am sorry, that my last PR didn't worked and sorry for wasting your time and requesting your review once again.

I have done some testing with the Address Sanitizer on the tests that failed on the buildbot. They work now.

I couldn't run `check-llvm` suite since I have limited computing resources (There are some OCaml binding tests, that fail even before my patch on my machine. When using a sanitizer build these failure logs are much larger. My machine just freezes. (It reports some missing symbols and crashes :( ) ).

https://github.com/llvm/llvm-project/pull/159379