[llvm] [mlir] [IR] Remove llvm.strip.invariant.group intrinsic (PR #225399)

[Antonio Frighetto via llvm-commits]

https://github.com/antoniofrighetto approved this pull request.

LGTM, nice!

(Minor nits: there are few other places in tests we could drop the intrinsic, including under BasicAA and CGP. Also s/strip.invariant.group// in Value.h and ValueTracking.h).

https://github.com/llvm/llvm-project/pull/225399