[llvm] [BOLT] Provide backwards compatibility for YAML profile with std::hash (PR #74253)

[Amir Ayupov via llvm-commits]

aaupov wrote:

> We can likely have a couple of binary/YAML test cases that verify backwards compatibility

Added a YAML test checking backwards compatibility. It reuses the test `bolt/test/X86/reader-stale-yaml.test` and its input (`bolt/test/X86/Inputs/blarge_profile_stale.yaml`) from before xxh diff.

https://github.com/llvm/llvm-project/pull/74253