Add Job duration

[ThomasPasquali]

Add a duration/runtime field to Job

[Sasso0101]

Instead of adding just a duration field, it might be more general to introduce a config field on the Job object. This config could be typed (e.g., Local, PBS, or Slurm), with each type encapsulating the relevant scheduler configuration parameters for that job.

That way, fields like duration/runtime, queue, memory, GPUs, etc. would all live inside the scheduler-specific config, keeping the Job interface cleaner.

[ThomasPasquali]

I agree but:

1. If we move jobs metadata to SQLite, we could create two Job interfaces: one ORM-like (with the full fields set) and on more user friendly
2. We shall also think about a better flow to gather results from different remotes. If you have metadata only available on remote clusters, copy-pasting the SbatchMan project is not enough (I had this need few times)