[InstCombine] limit icmp fold with sub if other sub user is a phi

This is a hacky fix for:
https://github.com/llvm/llvm-project/issues/54558

As discussed there, codegen regressed when we opened up this transform
to allow extra uses ( 61580d09 ), and it's not clear how to
undo the transforms at the later stage of compilation.

As noted in the code comments, there's a set of remaining folds that
are still limited to one-use, so we can try harder to refine and
expand the limitations on these folds, but it's likely to be an
up-and-down battle as we find and overcome similar regressions.

Differential Revision: https://reviews.llvm.org/D122909