Makes `InstructionSelector.h`/`InstructionSelectorImpl.h` generic so the match tables can also be used for the combiner.
Some notes:
- Coverage was made an optional parameter of `executeMatchTable`, combines won't use it for now.
- `GIPFP_` -> `GICXXPred_` so it's more generic. Those are just C++ predicates and aren't PatFrag-specific.
- Pass the MatcherState directly to testMIPredicate_MI, the combiner will need it.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D153755
1fe7d9c799