Automatically determine namespace and queue name when submitting jobs

Goals:

- User does not have to specify a Kueue queue name as part of `SchedulingOptions` (that attribute can actually be removed).
- Backend determines Kubernetes namespace and Kueue local queue from the project that a job is submitted in.

Implementation notes:

- This implies that the backend will require cluster-wide Kubernetes RBAC permissions, not just for a single namespace.