[clangd] Highlight typedefs to template parameters as template parameters

Summary:
Template parameters were handled outside `addType`, this led to lack of highlightings for typedefs
to template types.

This was never desirable, we want to highlight our typedefs as their underlying type.
Note that typedefs to more complicated types, like pointers and references are still not highlighted.

Original patch by Johan Vikström.

Reviewers: hokein, jvikstrom

Reviewed By: hokein

Subscribers: nridge, javed.absar, kristof.beyls, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D66516

llvm-svn: 371379