[Enhancement] let's not hardcode "cluster-autoscaler.kubernetes.io/safe-to-evict=false" for all etcd

[swapnilgm]

Feature (What you would like to be added):
etcd-druid should not hardcode the annotation "cluster-autoscaler.kubernetes.io/safe-to-evict=false" on etcd pods and let user configure it using annotation field in CRD.

Motivation (Why is this needed?):
Not every etcd is critical to system. The above mentioned annotation is specific to cluster-autoscaler and not etcd. Depending on the use of etcd CRD creator should have choice to add this annotation.
From gardener's POV, this etcd-main is critical but etcd-events is not that critical. So, the annotation should be set for etcd-main but not etcd-events. In future, we thought of deploying etcd for cilium networking extension, there also probably this annotation might not be required.

Approach/Hint to the implement solution (optional):
Remove the annotation from https://github.com/gardener/etcd-druid/blob/master/charts/etcd/templates/etcd-statefulset.yaml#L30.