syntax-highlighter: Update scip and add syntect->scip conversion

Created by: tjdevries

Nothing should be changed for the frontend in this PR. This is a purely additive PR for updates to syntax highlighter and adding a new /scip endpoint to syntax-highlighter

cc @olafurpg @fkling

Originally: https://github.com/sourcegraph/sourcegraph/pull/39264

Test plan

• Can run syntax highlighter and normal workflows and get exactly same results as before