Eventarc support for creating triggers for direct events from Firebase Authentication

## Feature Feature Eventarc support for[creating triggers](https://cloud.google.com/eventarc/standard/docs/event-providers-targets#triggers)for [direct events from Firebase Authentication](https://cloud.google.com/eventarc/docs/reference/supported-events#firebase-auth)is available in [Preview](https://cloud.google.com/products#product-launch-stages).