[llvm] [Debug] Add support for multi-level line support (PR #211390)

[via llvm-commits]

zhangweize9-cyber wrote:

> Thanks for opening this PR - now that this is past the draft phase, could this be broken up into multiple patches? I think it could reasonably be split in a few places, e.g. add metadata types | handle use of new metadata types in IR | backend emission.

Agreed. I also feel that we can break down the process into multiple sub-PRs based on functionality or the problem to be solved.

https://github.com/llvm/llvm-project/pull/211390