Description

Goal: Render search results faster

Reason:

• Highlighting code takes noticeably longer than fetching file contents. One of the issues with the search results page is that we often see pop-in as we try to fetch new results (See video below). We should be able to solve that by immediately rendering formatting code and enhancing with highlighting.
• It would be faster to run two parallel queries, one to fetch the current code and immediately render, and one to fetch the highlighted code and enhance the render.
• We can reasonably say that code will generally always render fast in this way, so we can remove the loading spinner between files and have a much more editor-like experience.

Related PR: https://github.com/sourcegraph/sourcegraph/pull/39563

A/C

• Fetch file contents that has formatting but not highlighting. This will allow us to improve performance without introducing any layout shifts to the UX.
• Feature flag this to experiment internally

/cc @taylorsperry @muratsu