[llvm-branch-commits] [Transforms] Delete loop-extract pass (PR #214252)

[Aiden Grossman via llvm-branch-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/214252

This was only used by bugpoint as far as I can tell, which was deleted
in 9d5574dda60151dcd1eb6f315c20e4d9120596f9. Given it is not used
anywhere, remove it.

I'm also not sure it's super useful for downstreams. When we were doing
a research project during my undergrad that needed loop etraction, we
ended up writing our own utilities to do this for reasons that I cannot
remember exactly.