[llvm] [BOLT] Simplify RAState helpers (NFCI) (PR #162820)

[Gergely Bálint via llvm-commits]

bgergely0 wrote:

I changed the error handling to mirror what ADRRelaxationPass does: set a `PassFailed` static bool on error, and `createFatalBOLTError()` at the end, if any threads failed.

https://github.com/llvm/llvm-project/pull/162820