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

[Christian Kandeler via cfe-commits]

ckandeler wrote:

A really nice feature that I would love to see go in. But note that there are a number of test failures:
```
Failed Tests (4):
  Clangd Unit Tests :: ./ClangdTests/DiagnosticTest/ClangTidySelfContainedDiags
  Clangd Unit Tests :: ./ClangdTests/DiagnosticTest/ClangTidySelfContainedDiagsFormatting
  Clangd Unit Tests :: ./ClangdTests/IncludeFixerTest/Typo
  Clangd Unit Tests :: ./ClangdTests/IncludeFixerTest/UnresolvedSpecifierWithSemaCorrection
```
You need to adapt the expected fix suggestions accordingly.

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