Add status field how many process groups are reconciled and how many are expected

[johscheuer]

What would you like to be added/changed?

I think it would be useful to provide this information in our status of the cluster resource and show it when using kubectl e.g. something like this:

NAME           GENERATION   RECONCILED   AVAILABLE   FULLREPLICATION   VERSION   AGE    ProcessGroups
test-cluster   2            1            true                          6.3.23    4m53s  16/16

This would be useful for debugging purposes and the operator already has all the required information we probably just have to add an additional field to the status and calculate this value.