[llvm] [AMDGPU][NPM] Support -regalloc-npm options (PR #129035)

[Christudasan Devadasan via llvm-commits]

cdevadas wrote:

> > I would prefer generic regalloc pipeline tunning options, X86 backend also has the same feature request, but it is related to generic builder design. I'm fine with this change if AMDGPU maintainers approve it.
> 
> I suppose we would need a TargetMachine hook to populate the filter functions and names to do that

@optimisan, support the generic style `-regalloc-npm="greedy<sgpr>,fast<wwm>"` so that targets can have filters to support specific RA options. First, introduce the TM hook for the filter.

https://github.com/llvm/llvm-project/pull/129035