Feature/increase worker count

[MKoesters]

Adresses #718

This PR allows to increase the number of worker nodes of an already existing cluster.

In order to increate worker count, change the number of workers in the config and reapply the config using the -cid CLI argument of an existing cluster.

Currently, only increasing worker node count is supported, other attributes cant be updated yet.
That would probably require a more sophisticated approach.

@XaverStiensmeier Would love to have some feedback from your side

I did test this by increasing the worker count of a running cluster.
I ended up with an additional, functional node in the same partition.

[XaverStiensmeier]

Looks great!

I am on holidays starting tomorrow and will not have the time to review it before, but while it takes a different approach then I had in mind, I feel like it is also a valid implementation; without using the existing update route. I will take a closer look once I am back.

[XaverStiensmeier]

I am still convinced that such a future change of the worker count should not be part of the regular create command, but of the update command: bibigrid/core/actions/update.py

This also avoids overloading the create command which might confuse users. What do you think?

[MKoesters]

I agree. I already implemted that change and thought that ive already pushed that here.
Apparently I did not.
Ill do this in the beginningoft next week and ping you