KAFKA-19276: Trigger rebalance for streams config update [WIP]

[UladzislauBlok]

Work in progress. Doc and test are on my list

Create listener for config updates. Now we could react on config updates in impls of GroupConfigListener (e.g. StreamsRebalanceConfigListener) and take concrete actions, e.g. set triggerRebalance flag to true and check it in client (GroupMetadataManager) to trigger rebalance.

I've tried to keep GroupConfigListener generic and I found three potential types of action implementations could do:

1. Set flag (mark something) and wait until client check that and takes an action (current case)
2. Listener takes an actions on it's own
3. State of listener was not changed, it's like opposite action (or let's say lack of action) for case 1
   To create generic return type for all three cases I chose an enum as return type, so we can describe all the cases, e.g. of future state:

public enum ConfigUpdateEvent {
    // Client Actions Required
    REBALANCE_REQUIRED,

    // Actions were taken by listener
    ERROR_LOGGED... or something

    // Statuses where no further action is needed by client or observer
    UNCHANGED;
}