[llvm] [X86][IPRA] Add getIPRACSRegs since frame registers are risked to be optimized out. (PR #109597)

[Reid Kleckner via llvm-commits]

https://github.com/rnk approved this pull request.

I'm not a major IPRA stakeholder, so there might be a better owner, but I think correctness comes before performance tradeoffs, so we should go ahead and land this and work to optimize from a less buggy state. Thanks for the fix!

https://github.com/llvm/llvm-project/pull/109597