[clangd] Loading TokenColorRules as a class mapping the rules to their associated clangd TextMate scope index.
Summary: Loads a mapping of the clangd scope lookup table scopes to the most specific rule with the highest "precedence" on initialize. Preprocesses into a class so it's simple/fast to access when doing the actual coloring later.
Reviewers: hokein, ilya-biryukov
Subscribers: MaskRay, jkorous, arphaman, kadircet, cfe-commits
Differential Revision: https://reviews.llvm.org/D65856