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

[Amara Emerson via llvm-commits]

aemerson wrote:

You're right, I thought we could find some C++ magic to make this ergonomic but after trying myself I came up short. At least not without a restructuring of the `LegalizeRuleSet` infrastructure.

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