[GlobalISel] Generalize `InstructionSelector` Match Tables

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