[clangd] Make use of syntax tokens in ReplayPreamble

Summary: Replace usage of RawLexer with syntax tokens inside ReplayPreamble.

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74842