Allow to define how may Pods should automatically replaced

[johscheuer]

Currently we only replace one failed Pod when we enable the feature. I think it makes sense to allow the user to specify how many Pods should/can be replaced.

[johscheuer]

Think about that a little bit we would implement that as some kind of a max inflight replacements which would be the upper limit of replacements for the automatic replacements. If the user would specify 5 that means the controller will evaluate how many process groups are currently marked for removal and if the limit is not reached the controller can replace as many process groups until the limit is reached. A concrete example a user sets the limit to 5 and the operator has 3 ongoing replacements, that means the operator will replace at most 2 process groups.