v2.3.0: Adds deleted collection entity listener

Adds a listener to handle deletion of entities in to-many collections.

This change introduces a mechanism to properly delete entities
that are removed from a to-many collection during form processing.
It ensures that orphaned entities are removed from the database,
preventing data inconsistencies. It finds the instance of the listener if exists and calls its addDeletedEntity method to persist a deleted entity.
Also, the onAfterMapToForm method in BaseForm is updated to pass the entity to the event.