[llvm] [SandboxVec][DAG] MemDGNode for memory-dependency candidate nodes (PR #109684)

[via llvm-commits]

vporpo wrote:

Now that the Interval is available there is no need for the custom iterator that was implemented in this patch. I was planning to do this cleanup in the follow-up patch, but it's probably best to do this here since it simplifies the code of this patch a bit.

https://github.com/llvm/llvm-project/pull/109684