[clang-tools-extra] [clangd] Add code action to suppress clang-tidy diagnostics (PR #188796)

[Sirui Mu via cfe-commits]

Lancern wrote:

> > A previous PR #114661 attempted to land similar feature, but it ends up being closed by its author.
> 
> In that patch, in the comments, there was a suggestion to use "feature module" for this implementation [#114661 (review)](https://github.com/llvm/llvm-project/pull/114661#pullrequestreview-2413065542). Can you please address it? Example of feature modules implementation can be found in tests (e.g. here https://github.com/llvm/llvm-project/blob/main/clang-tools-extra/clangd/unittests/FeatureModulesTests.cpp#L27 )

Thanks for the feedback.

I'm trying to migrate changes in this PR to a feature module. The issue is that `ParsedAST::build` has a non-trivial amount of code building a ClangTidy context for identifying and processing ClangTidy diagnostics, which is not accessible in a feature module. I don't know whether it's possible to build a ClangTidy context in a feature module (specifically, in an AST listener) without a non-trivial refactor attempt.

Also, I notice that there are currently no in-tree usage of feature module. Is it really preferable to introduce the change as a feature module?

https://github.com/llvm/llvm-project/pull/188796