KAFKA-18538: Add Streams membership manager (apache#18551)

The Streams membership manager is used client-side in the
background thread of the async consumer. For each member
/consumer, it is responsible for:
* keeping the member state,
* keeping assignments for the member,
* reconciling the assignments of the member -- for example
when tasks need to be revoked before other tasks are assigned
* requesting invocations of assignment and revocation callbacks
by the stream thread.

The Streams membership manager is called by the background thread of
the async consumer, directly in its event loop and from the
 Streams group heartbeat request manager. The Streams membership
manager uses the Streams rebalance events processor to request
assignment/revocation callback in the stream thread.

Reviewers: Lucas Brutschy <[email protected]>, Bill Bejeck <[email protected]>

Author: cadonna

clients/src/main/java/org/apache/kafka/clients/consumer/internals/AbstractMembershipManager.java

@@ -159,7 +159,7 @@ public abstract class AbstractMembershipManager<R extends AbstractResponse> impl
     /**
      * If the member is currently leaving the group after a call to {@link #leaveGroup()} or
      * {@link #leaveGroupOnClose()}, this will have a future that will complete when the ongoing leave operation
-     * completes (callbacks executed and heartbeat request to leave is sent out). This will be empty is the
+     * completes (callbacks executed and heartbeat request to leave is sent out). This will be empty if the
      * member is not leaving.
      */
     private Optional<CompletableFuture<Void>> leaveGroupInProgress = Optional.empty();