[Zone Decommission] Removal of nodes in decommissioned zone

[gbbafna]

Design Proposal

#3402

Feature Proposal

#3917

Describe the solution you'd like

1. Remove all the nodes in decommissioned zone.
2. Make sure that they don't join back again . We can add one more Join Validator in here to reject joins coming from nodes in decommissioned zone and Kill-Switch for Decommission is Off.

[imRishN]

Implemented as part of #4084 . Can close the issue now