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

[Tor Shepherd via cfe-commits]

torshepherd wrote:

@HighCommander4 I've pushed up the change that doesn't allow conflicting fixits. I'll now be smoke-testing this over the coming weeks while I work, but consider it ready for review again whenever you have a chance

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