### Apache Airflow Provider(s)

google

### Versions of Apache Airflow Providers

apache-airflow-providers-google~=5.0

### Apache Airflow version

2.1.3 (latest released)

### Operating System

MacOS Big Sur

### Deployment

Astronomer

### Deployment details

_No response_

### What happened

The CloudSqlProxyRunner queries the Airflow DB directly to retrieve the GCP connection.

https://github.com/apache/airflow/blob/7b3a5f95cd19667a683e92e311f6c29d6a9a6a0b/airflow/providers/google/cloud/hooks/cloud_sql.py#L521

### What you expected to happen

In order to not break when using connections stored in external secrets backends, it should use standardized methods to retrieve connections and not query the Airflow DB directly.

### How to reproduce

Use a CloudSQLDatabaseHook with `use_proxy=True` while using an external secrets backend.

### Anything else

Every time

### Are you willing to submit PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

airflow/providers/google/cloud/hooks/cloud_sql.py
self,
        gcp_cloudsql_conn_id: str = 'google_cloud_sql_default',
        gcp_conn_id: str = 'google_cloud_default',
        default_gcp_project_id: Optional[str] = None,
    ) -> None:
        super().__init__()
        self.gcp_conn_id = gcp_conn_id
        self.gcp_cloudsql_conn_id = gcp_cloudsql_conn_id
        self.cloudsql_connection = self.get_connection(self.gcp_cloudsql_conn_id)
        self.extras = self.cloudsql_connection.extra_dejson
        self.project_id = self.extras.get('project_id', default_gcp_project_id)  
        self.instance = self.extras.get('instance')  
        self.database = self.cloudsql_connection.schema  
        self.location = self.extras.get('location')  
        self.database_type = self.extras.get('database_type')  
        self.use_proxy = self._get_bool(self.extras.get('use_proxy', 'False'))  
        self.use_ssl = self._get_bool(self.extras.get('use_ssl', 'False'))  
        self.sql_proxy_use_tcp = self._get_bool(self.extras.get('sql_proxy_use_tcp', 'False'))