Send Key hash range change events to consumers in Key_Shared subscription.

[codelipenghui]

Master issue: #4077
Is your feature request related to a problem? Please describe.
Send Key hash range change events to consumers in Key_Shared subscription.

[zubchenok]

Please up.
Unable to maintain a local consumer cache if I don't know when a key is not served by the consumer any more.

[lhotari]

When adding this feature, would it be possible to support this in the asynchronous API of the Pulsar Java Client too? I guess race conditions could be problematic unless pending receives are completed with exceptions?

[codelipenghui]

@lhotari We have a consumer events listener https://github.com/apache/pulsar/blob/6704f12104219611164aa2bb5bbdfc929613f1bf/pulsar-client-api/src/main/java/org/apache/pulsar/client/api/ConsumerEventListener.java, users need to register a listener for getting the new events of the consumer

pulsar/pulsar-client-api/src/main/java/org/apache/pulsar/client/api/ConsumerBuilder.java

Line 410 in ef06691

ConsumerBuilder<T> consumerEventListener(ConsumerEventListener consumerEventListener);