[clangd] Added highlighting for class and enum types.

Summary: Added highlighting for non-builtin types using VisitTypeLoc. Ignoring namespace qualifiers as for now.

Reviewers: hokein, sammccall, ilya-biryukov

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

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64257

llvm-svn: 365602