### Description

Support mounting to multiple namespaces with the Hashicorp Vault Secrets Back-end

### Use case/motivation

As a data engineer I wish to utilize secrets stored in multiple mount paths (to support connecting to multiple namespaces)  without having to mount to a higher up namespace.

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] 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)

mock_client = mock.MagicMock()
        mock_hvac.Client.return_value = mock_client
        mock_client.is_authenticated.return_value = False
        kwargs = {
            "connections_path": "connections",
            "mount_point": "airflow",
            "auth_type": "token",
            "url": "http://127.0.0.1:8200",
            "token": "test_wrong_token",
        }
        with pytest.raises(VaultError, match="Vault Authentication Error!"):
            VaultBackend(**kwargs).get_connection(conn_id="test")
    def test_auth_type_kubernetes_with_unreadable_jwt_raises_error(self):