Batched EventListenerDrivers not getting flushed if not listening on FinishStructureRunEvent

[vachillo]

• I have read and agree to the contributing guidelines.

Describe the bug
When using a batched EventListenerDriver, the last batch does not get flushed if it does not hit the max batch size. When a FinishStructureRunEvent is emitted, it uses flush=True, but if the listener is not listening on this event, it does not get flushed

To Reproduce

driver = GriptapeCloudEventListenerDriver(batched=True, batch_size=100)  # or any other driver

def stream_handler(event: CompletionChunkEvent) -> dict:
    return {
        "text": event.token,
    }

listener =  EventListener(
    stream_handler,
    event_types=[CompletionChunkEvent],
    driver=driver,
)

EventBus.add_event_listener(listener)

agent = Agent(stream=True).run("hello")

Expected behavior
There should be a signal to flush all EventListeners, regardless of the events they are listening on.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Version [e.g. 0.5.1]

Additional context
Add any other context about the problem here.