[clangd] Added highlighting for the targets in typedefs and using.

Summary:
In `typedef int A` the `A` was not highlighted previously.

This patch gives `A` the same kind of highlighting that the underlying type has (class/enum) (which in this example is no special highlighting because builtins are not handled yet)
Will add highlightings for built ins in another patch.

Reviewers: hokein, sammccall, ilya-biryukov

Subscribers: MaskRay, jkorous, arphaman, kadircet, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64754

llvm-svn: 366207