[clangd] Simplify semantic highlighting visitor

Summary:
- Functions to compute highlighting kinds for things are separated from
  the ones that add highlighting tokens.
  This keeps each of them more focused on what they're doing: getting
  locations and figuring out the kind of the entity, correspondingly.

- Less special cases in visitor for various nodes.

This change is an NFC.

Reviewers: hokein

Reviewed By: hokein

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

Tags: #clang

Differential Revision: https://reviews.llvm.org/D67341

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@372008 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed