[llvm] [LLVM] Add `llvm.masked.compress` intrinsic (PR #92289)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> @arsenm could you let me know how to proceed with the GlobalISel stuff on Arch64? I can also move this to the follow-up PR ([temporary version here](https://github.com/lawben/llvm-project/pull/1)), as that covers AArch64 explicitly anyway.

Separate PR for the legal case makes sense 

https://github.com/llvm/llvm-project/pull/92289