[llvm] [SampleFDO] Improve stale profile matching by diff algorithm (PR #87375)

[Lei Wang via llvm-commits]

wlei-llvm wrote:

In the new change:
- Update  the `IRAnchors`, `ProfileAnchors` to use `Anchor` as map value. 
- Some variable renaming. 

https://github.com/llvm/llvm-project/pull/87375