Notebook startup timeout

[gweis]

Reduce timeout waiting for notebook to startup. With a reduced timeout we may be able to return quicker to an end user in case notebook start up fails for some reason.

Important thing here is that the initial sync fo the workspace has to be factored into the time out. We have to make sure that a full download from object store can happen before the time out expires.
Or we have to change how we sync it (e.g. not using initcontainers) but then have to be careful with readiness and liveness probes