[llvm] [RegAlloc] Scale the spill weight by the weight of register class (PR #113675)

[Pengcheng Wang via llvm-commits]

wangpc-pp wrote:

I believe this is the right direction (and I think most people have echoed the same thought). Now this change is applied to the infrastructure code, which means all the targets will be influenced. I have a rough scan of the diffs, I think most of them are positive changes, but I need more eyes on other targets besides RISC-V.

https://github.com/llvm/llvm-project/pull/113675