[llvm] Reapply "[DomTreeUpdater] Move critical edge splitting code to updater" (PR #119547)

[Quentin Colombet via llvm-commits]

qcolombet wrote:

> This reverts commit a28d49b7b54b85b4b2e344a0d4ebc9d511562fee. Use traditional way to update post dominator tree. When splitting critical edges, the post dominator tree may change its root node, and `setNewRoot` only works in normal dominator tree...
> 
> https://github.com/llvm/llvm-project/blob/6c7e5827eda26990e872eb7c3f0d7866ee3c3171/llvm/include/llvm/Support/GenericDomTree.h#L684-L687

What did you change in the new version of the patch to avoid this problem?

https://github.com/llvm/llvm-project/pull/119547