[llvm] [VPlan] Add initial CFG simplification, removing BranchOnCond true. (PR #106748)

[David Sherwood via llvm-commits]

https://github.com/david-arm commented:

I think the idea of cleaning up the CFG makes a lot of sense, but I am a bit confused by some of the changes and how this works. I'm probably missing something, but I left a few comments anyway!

https://github.com/llvm/llvm-project/pull/106748