### 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
"""
        Validates sockets path length.
        :return: None or rises AirflowException
        """
        if self.use_proxy and not self.sql_proxy_use_tcp:
            if self.database_type == 'postgres':
                suffix = "/.s.PGSQL.5432"
            else:
                suffix = ""
            expected_path = "{}/{}:{}:{}{}".format(
                self._generate_unique_path(), self.project_id, self.instance, self.database, suffix
            )
            if len(expected_path) > UNIX_PATH_MAX:
                self.log.info("Too long (%s) path: %s", len(expected_path), expected_path)
                raise AirflowException(
                    "The UNIX socket path length cannot exceed {} characters "
                    "on Linux system. Either use shorter instance/database "
                    "name or switch to TCP connection. "
                    "The socket path for Cloud SQL proxy is now:"
                    "{}".format(UNIX_PATH_MAX, expected_path)
                )
    @staticmethod
    def _generate_unique_path() -> str: