[RFC][GlobalISel] Overhauled MIR Patterns Support for Combiners

See https://discourse.llvm.org/t/rfc-overhauled-mir-patterns-for-globalisel-combiners/72264

This is a complete overrhaul of the recently-added GlobalISel Match Table backend which adds
support for MIR patterns for both match and apply patterns.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D156315