Add support for batching event delivery in @EventListener and @TransactionalEventListener

Description

Currently, Spring invokes @EventListener and @TransactionalEventListener methods once per published event. When multiple events of the same type are published within a single transaction, each results in a separate listener invocation.

It would be useful to support batched event delivery, allowing listeners to receive all events of the same type published during the transaction as a single List.

Use Case

Within a transactional service, multiple updates are performed, and corresponding domain events are published.
Each event triggers a separate listener call, resulting in multiple update statements and row locks.

Batch delivery would allow a single @TransactionalEventListener(phase = BEFORE_COMMIT) method to process all pending events together, enabling a single batched update.

Proposed Enhancement

Support for batched listener signatures such as:

@TransactionalEventListener(phase = TransactionPhase.BEFORE_COMMIT)
public void handleEvents(List<AppEvent> events) {
    batchUpdate(events);
}

The framework could accumulate events per transaction (e.g., using TransactionSynchronizationManager) and dispatch them together before commit.

Benefits

1. Reduces redundant database updates
2. Minimizes row locking and improves transaction efficiency
3. Simplifies batching logic for domain event processing

Start with the @EventListener and @TransactionalEventListener handling described in the issue, then examine how TransactionSynchronizationManager could collect events during a transaction. Done means listeners accepting List can receive same-type events together, including BEFORE_COMMIT transactional delivery, while preserving existing single-event behavior.