Add Controller APIs to add/remove/update subscriber from multiple Streams.

[pbelgundi]

Problem description
Current for ConsumptionBasedRetention we have APIs to add/remove a Subscriber from a Single Stream.
But if a Reader Group reads from multiple Streams, the subscriber addition/deletion/update to all Streams in the ReaderGroup Configuration needs to happen atomically.

Problem location
Controller

Suggestions for an improvement
This can be done by adding the following 4 new APIs to controller:

addSubscriberToStreams(List < Stream > , String subscriber)
This internally would use the ControllerEventProcessor framework to make sure the subscriber is added to all Streams (at least eventually)

b. deleteSubscriberFromStreams(List < Stream > , String subscriber)
Same like (a)

c. UpdateSubscribersForStreams(Map < Stream, String, opr >)
Add/delete a subscriber from multiple streams (add to some/delete from some) and complete all updates atomically.

d. UpdateSubscriberStreamcut(Map < Stream, StreamCut >)
Add/delete subscriber from a stream and complete all updates atomically.
All Unit and Integration Tests should pass

[pbelgundi]

This is not needed anymore.