chore: cleanup legacy server code

[robinlindh]

Since now we've completed the deployment of 0.3.0 and all seems to work good with Rust compute node, there is no reason to keep the old golang code around anymore. It's mostly just confusing, so I'm removing that now.

• Remove all the old server code that's no longer used (from golang)
• Remove extra dockerfiles which still used the old server code. We can add them back using Rust base image if needed later on.
• Update the devcontainer to build and use rust server, and some utility scripts to work inside the dev container.
• Remove old helper scripts from long ago which anyway don't work anymore.