[llvm] [GISel][CombinerHelper] Combine and(trunc(x), trunc(y)) -> trunc(and(x, y)) (PR #89023)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > Should move this to tablegen patterns
> 
> @arsenm Which file would this be? I had tried searching for something like this originally but couldn't find anything.

https://llvm.org/docs/GlobalISel/MIRPatterns.html

It would go in the generic Combine.td, just with most of the C++ boilerplate replaced with tablegen 

https://github.com/llvm/llvm-project/pull/89023