[lld] [lld][ELF] Implement merged .debug_names section. (PR #86508)

[via llvm-commits]

cmtice wrote:

> > (Reading. I find `ELFT::TargetEndianness` too long. Proposed #86604 to allow `ELFT::Endian`. No action needed yet)
> 
> We ended up with `ELFT::Endianness`. The next update can switch to `ELFT::Endianness`

Done: I've switched to using ELFT::Endianness.

https://github.com/llvm/llvm-project/pull/86508