[llvm] Reland "[Support] Assert that DomTree nodes share parent"" (PR #102782)

[Paul Kirth via llvm-commits]

ilovepi wrote:

> @ilovepi I was able to reproduce the (or a similar) problem in a stage2 clang build, and can say that #103302 fixed the problem for me.

Thanks!

https://github.com/llvm/llvm-project/pull/102782