Many Pravega Spec parameters are still not updatable at runtime

[SrishT]

Description

There are many Pravega Spec parameters still remaining which cannot be updated once the pravega cluster has been created. All the spec fields other than the the version, replica count, DNS name, JVM options as well as the pravega options still come under this category. While not allowing updates on some parameters might make sense, it will be necessary to allow updates to a few others including controllerResources, segmentStoreResources, segmentStoreEnvVars, segmentStoreSecret etc.

Importance

must have

Location

pkg/controller/pravegacluster/pravegacluster_controller.go

Suggestions for an improvement

The operator reconcile logic would need to be modified so that updates to necessary fields are allowed during the lifetime of the cluster.
A maintenance mode can be added to stop operator from watching all resources and allow the user to make any changes to recover the cluster.