FABAuthManager migrate endpoints to FastAPI

### Description
Depends on: https://github.com/apache/airflow/issues/44847

FABAuthManager defines extra flask endpoints.

As part of the migration to FastAPI these endpoints need to be converted to FastAPI.

Endpoints located in `airflow/providers/fab/auth_manager/api_endpoints` needs to be converted to FastAPI. (Duplicated for now, legacy flask endpoint will be removed later)

