[llvm] [clang] [clang-tools-extra] [SimplifyCFG] Prevent merging cbranch to cbranch if the branch probability from the first to second is too low. (PR #69375)

[Valery Pykhtin via cfe-commits]

vpykhtin wrote:

> I've been puzzling over the rationale for looking at `MD_unpredictable`. How can a branch that is heavily biased to one side be unpredictable?

I'm curious either, I just decided to follow a 'standard' pattern in this source.

https://github.com/llvm/llvm-project/pull/69375