[llvm] [LLVM] Add option to store Parent-pointer in ilist_node_base (PR #94224)

[Danial Klimkin via llvm-commits]

dklimkin wrote:

H Stephen,

We ran into some issues with `getParent()` and `getNodeBaseParent()` returning a const pointer rather than a pointer to a const, resulting in iterators returned also not being const. I'll send a PR with a workaround but adding a note here in case you have a better solution in mind.

https://github.com/llvm/llvm-project/pull/94224