More flexible editor serving

### Description

Right now the only ways to serve flowfuse are:
- subdomains configured via nginx proxy (driver-docker)
- random ports (driver-localfs)

But this means that you would have to shift your project to nginx-proxy to use flowfuse.

It would be nice to be able to:
- serve editors from the main dashboard through a subpath (i.e. without an external reverse proxy)
- would it be trivial to forward traffic via `/editors/{app-name}/*`?
- configure alternative reverse proxies in driver-docker (traefik uses labels instead of environment variables)

### Which customers would this be available to

Everyone - CE/Starter/Team/Enterprise

### Have you provided an initial effort estimate for this issue?

I am not a FlowFuse team member