Disable fault zone as an entity for cleaner operation

[qqu0127]

Is your feature request related to a problem? Please describe. When upgrading a cluster, it is a good practice to upgrade each fault zone one by one. But Helix does not support disabling a whole fault zone yet.

Describe the solution you'd like We'd want to implement the feature that allows disable a fault zone as an entity, so that all instances (now and in the future) in the zone are effectively disabled. In this way the operation could be atomic and there is no need to track status of every single instance. There is also opportunity for instance validation related code refactor and cleanup.

Additional context Add any other context or screenshots about the feature request here.