[llvm] [profcheck] Add heuristical profile metadata for lowering table-based cttz. (PR #161898)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 commented:

Is the 100:1 ratio derived from something other than intuition? It's probably fine, especially since most passes don't make use of exact numerical information, but having a (documented) basis for this would be good, especially if someone wants to follow up in the future.

https://github.com/llvm/llvm-project/pull/161898