[Feature] Defragmentor of backup-restore should also consider the etcd db size along with scheduled defrag

[ishan16696]

Feature (What you would like to be added):
Defragmentor logic of backup-restore should also consider the etcd db size along with schedule time of defragmentation and if Defragmentor observed that etcd db size has crossed the certain limit(say 7Gi) which is close to etcd db quota bytes then it should trigger the out-of-schedule defragmentation on etcd so that etcd db size won't crosses the practical limit of 8Gi.

Motivation (Why is this needed?):
It has been observed that sometimes etcd's db size abruptly increases and cross the practical limit of 8Gi which leads to unavailability of etcd cluster. To resolve this we require the manual intervention to trigger the defragmentation on etcd, to avoid this manual intervention our defragmentor should smart enough to detect this and trigger the out-of-schedule defragmentation on etcd.

Approach/Hint to the implement solution (optional):

[ishan16696]

This feature can also mitigate NOSPACE alarm #531

[shreyas-s-rao]

/assign @ishan16696