[llvm] [LLVM][DWARF] Add support for monolithic types in .debug_names (PR #70515)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> (if we don't get this perfect by Friday, it's probably close enough I'm happy to approve and I can do some follow-ups post-commit, FWIW)

I know very little about `.debug_names`, but I am a stakeholder as a lld/ELF patch needs this to show its effect.

If you want to approve and land this and do follow-ups, it this looks great to me! I just need something I can play with to better review the lld/ELF patch.

(As we now need `[fixup! fixup! fixup! fixup! fixup! fixup! fixup! fixup! fixup!]`, I guess it should be fine to just squash them and rebase (this patch doesn't apply on main now)

https://github.com/llvm/llvm-project/pull/70515