[clang-tools-extra] [clangd] Add 'apply all clangd fixes' and 'apply all '_' fixes' QuickFixes (PR #79867)

[Tor Shepherd via cfe-commits]

torshepherd wrote:

It's been a while since I looked at this, but from what I remember my attempt to fix the last part didn't quite work as expected. I can try to test it again, but I ended up just abandoning it at the time since I didn't really miss the functionality as much as I thought

https://github.com/llvm/llvm-project/pull/79867