[llvm] [DomTreeUpdater] Move critical edge splitting code to updater (PR #115111)

[NAKAMURA Takumi via llvm-commits]

chapuni wrote:

Seems failing to build `tools/llvm-readtapi/CMakeFiles/llvm-readtapi.dir/llvm-readtapi.cpp.o`

```
fatal error: error in backend: SmallVector unable to grow. Requested capacity (4294967296) is larger than maximum value for size type (4294967295)
```

See "stage3" in https://lab.llvm.org/buildbot/#/builders/164/builds/5423

In my private builder, I saw memory exhaust after a few minutes.

https://github.com/llvm/llvm-project/pull/115111