Extend the existing combine that handles bitcasting for fp-logic ops to also help remove logic ops across bitcasts to/from the same integer types.
This helps improve AVX512 predicate handling for D/Q logic ops and also allows DAGCombine's scalarizeExtractedBinop to remove some annoying gpr->simd->gpr transfers.
For the record I'm intending to commit this fold as a followup commit to the fix the temporary regression.