[llvm] [GlobalISel] Add boolean predicated legalization action methods. (PR #111287)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

We already have a legalIf, but that should be for complex predicates. This has the advantage of not actually adding it to the rule set for the subtarget 

https://github.com/llvm/llvm-project/pull/111287