[llvm] [BOLT][AArch64] Support cdsplit for AArch64 (PR #121475)

[Paschalis Mpeis via llvm-commits]

paschalis-mpeis wrote:

> For example using -split-strategy=cdsplit --dump-dot-all should crash regardless of architecture. On X86 one can indeed get a binary with hot/warm/cold sections, but I'm not sure to which extend this is due to luck. I would expect under some scenarios to hit this assertion with ICP, ShrinkWrapping, and TailDuplicatio

Regarding my earlier comment, I reference issue #123835, which is a crash with `ShrinkWrapping` and `cdsplit` on x86. In that particular case the reproducer is not deterministic. @aaupov [suggested](https://github.com/llvm/llvm-project/issues/123835#issuecomment-2605925949) to either disable one of the two optimizations.

I also became aware of reports where with Assertions=Off, `LongJmp` stucks due to `cdsplit` but the reasons were not obvious to end users. I've added a note on this earlier, for referencing.

IMHO, it's worth proceeding with a number of PRs here to gradually clear up the space of all `isCold` users. 

https://github.com/llvm/llvm-project/pull/121475