[clang-tools-extra] [clangd] Report reference to UsingType's target decl at the correct location (PR #186310)

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

> Update: it looks like for `foo` we have no highlighting without `typename` prefix (i.e. `typename A::foo abc;` `foo` is highlighted, `A::foo abc;` `foo` is not highlighted)

I think that's due to [this FIXME](https://searchfox.org/llvm/rev/b751719170fdba8c0b9c07b5b6a598e95baba580/clang-tools-extra/clangd/FindTarget.cpp#207-208).

> maybe we still should use `getNameLoc()` inside `VisitUnresolvedUsingTypeLoc()` because it gives correct position of `foo`

Done

https://github.com/llvm/llvm-project/pull/186310