[clangd] Validate clang-tidy Checks in clangd config.

Add instrumentation in ConfigCompile to validate that items in ClangTidy:[Add|Remove] correspond to actual clang-tidy checks.
If they don't a warning will be presented to the user.

This is especially useful for catching typos in the glob items.

Reviewed By: sammccall

Differential Revision: https://reviews.llvm.org/D92874