feat: move to code-server and patch in edit tagging

[Vtec234]

• Move from openvscode-server, currently stuck at 1.109.5, to code-server which is up to date with upstream at 1.122.1.
• Apply a patch to code-server (by building it from scratch ourselves) which allows tagging programmatic document change events with where they came from. This allows us to fully reliably distinguish our own edits during collaborative syncing and unbreaks Vim extensions, code actions, etc.
• Main disadvantage is that building VSC (twice - see the Dockerfile) makes our CI very heavy. A desirable followup might be to put that in its own, cached, CI step (or even another repo).