Add `event.received` trigger

[nielsrowinbik]

• Trigger name: event.received
• Title: Event received
• Description: Triggers when an event is received.
• Listens on: event domain.
• Note: The user has to select the event_type they want to listen to based on the selected entity.
• Note: Event entities are stateless and the trigger should have the same functionality as the button.pressed trigger added in Add button pressed trigger #158745, which means no trigger behaviour (any/first/all) configuration should be required.

Implementation notes

• Also, the trigger needs selector context to work for event entities to meet requirement that "user should be able to select the event_type they want to listen to based on the selected entity".