[llvm] [BOLT][AArch64] Handle OpNegateRAState to enable optimizing binaries with pac-ret hardening (PR #120064)

[Gergely Bálint via llvm-commits]

bgergely0 wrote:

Thanks for the approval @paschalis-mpeis !

I just pushed the last change I wanted, renaming the flag to `update-branch-protection`, in line with the discussion above. This way we can extend it in follow-up PR to introduce a "strict-mode", and include rewriting BTI, once support for that is ready.

https://github.com/llvm/llvm-project/pull/120064