[InstSimplify] Restrict a GEP transform to avoid provenance changes

This is a follow-up to D98588, and fixes the inline `FIXME` about a GEP-related simplification not
preserving the provenance.

https://alive2.llvm.org/ce/z/qbQoAY

Additional tests were added in {rGf125f28afdb59eba29d2491dac0dfc0a7bf1b60b}

Depends on D98672

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D98611