[Feature] Move status update to a separate controller in druid

[amshuman-kr]

Feature (What you would like to be added):
The main reconciliation loop in etcd-druid takes care of everything from updating the owned resources and updating the status in the Etcd resource. We should create a separate controller (still part of the etcd-druid controller manager) which reconciles only the status section of the Etcd resource.

Credit: @rfranzke ❤️

Motivation (Why is this needed?):
The main reconcilation loop is triggered only if the watch events pass some predicates. If the status update during the main reconcilation fails for any reason, the status in the Etcd resource might not be updated until the next gardener reconcilation event that matches the predicates.

Approach/Hint to the implement solution (optional):

[amshuman-kr]

cc @rfranzke

[rfranzke]

/normal

[abdasgupta]

/assign