### 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)

"wrap_info": None,
            "warnings": None,
            "auth": None,
        }
        kwargs = {
            "configs_path": "configurations",
            "mount_point": "secret",
            "auth_type": "token",
            "url": "http://127.0.0.1:8200",
            "token": "s.FnL7qg0YnHZDpf4zKKuFy0UK",
        }
        test_client = VaultBackend(**kwargs)
        returned_uri = test_client.get_config("sql_alchemy_conn")
        assert "sqlite:////Users/airflow/airflow/airflow.db" == returned_uri
    @mock.patch("airflow.providers.hashicorp._internal_client.vault_client.hvac")
    def test_connections_path_none_value(self, mock_hvac):
        mock_client = mock.MagicMock()
        mock_hvac.Client.return_value = mock_client
        kwargs = {
            "connections_path": None,
            "mount_point": "airflow",
            "auth_type": "token",
            "url": "http://127.0.0.1:8200",
            "token": "s.FnL7qg0YnHZDpf4zKKuFy0UK",
        }
        test_client = VaultBackend(**kwargs)
        assert test_client.get_conn_uri(conn_id="test") is None
        mock_hvac.Client.assert_not_called()
    @mock.patch("airflow.providers.hashicorp._internal_client.vault_client.hvac")
    def test_variables_path_none_value(self, mock_hvac):