[clang-tools-extra] [clangd] Resolve the dependent type from its single instantiation. Take 1 (PR #71279)

[Younan Zhang via cfe-commits]

zyn0217 wrote:

@HighCommander4 While at the `HeuristicResolver`, I think we may have a bug inside `HighlightingsBuilder` defined in `SemanticHighlighting.cpp`.

https://github.com/llvm/llvm-project/blob/6ed9a81f7ebd23f125867dd270785dd0e63043c6/clang-tools-extra/clangd/SemanticHighlighting.cpp#L592

I didn't see any other lines initializing this member. so we're always yielding `nullptr` from `H.getResolver` calls?

https://github.com/llvm/llvm-project/pull/71279