Replace Monaco with CodeMirror

Created by: fkling

This epic tracks outstanding work related to migrating from Monaco to CodeMirror. See RFC 637 for more information.

There are roughly three work streams:

• Use CodeMirror for the search query input (behind feature flag)
• Use CodeMirror for Notebooks
• Use CodeMirror anywhere else we use Monaco (behind feature flag)
  • The only other occurrences of Monaco are the settings editor and the batch changes editor.