[llvm] [BasicBlockSections] Propose a staleness detection method, checking the func cfg node num (PR #133244)

[Sriraman Tallam via llvm-commits]

tmsri wrote:

Could you say more about the design choice here of just using node count?  Looks like storing the hash of the entire CFG in some manner would me more meaningful.  You don't want to be too sensitive to IR changes, so hashing the entire IR might be too much.

https://github.com/llvm/llvm-project/pull/133244