[llvm] [DomTreeUpdater] Handle critical edge splitting (PR #100856)

[Jakub Kuderski via llvm-commits]

https://github.com/kuhar commented:

Could you wait a few days for me to review this?

> Unfortunately the performance of generic lazy updater is not so efficient for critical edge splitting (about +0.2%).

I remember this was the original reason for us leaving the 'manual' update mechanism around

https://github.com/llvm/llvm-project/pull/100856