### 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)

"destroyed": False,
                    "version": 1,
                },
            },
            "wrap_info": None,
            "warnings": None,
            "auth": None,
        }
        kwargs = {
            "connections_path": "connections",
            "mount_point": "airflow",
            "auth_type": "token",
            "url": "http://127.0.0.1:8200",
            "token": "s.7AU0I51yv1Q1lxOIg1F3ZRAS",
        }
        test_client = VaultBackend(**kwargs)
        returned_uri = test_client.get_conn_uri(conn_id="test_postgres")
        assert "postgresql://airflow:airflow@host:5432/airflow" == returned_uri
    @mock.patch("airflow.providers.hashicorp._internal_client.vault_client.hvac")
    def test_get_connection(self, mock_hvac):
        mock_client = mock.MagicMock()
        mock_hvac.Client.return_value = mock_client
        mock_client.secrets.kv.v2.read_secret_version.return_value = {
            "request_id": "94011e25-f8dc-ec29-221b-1f9c1d9ad2ae",
            "lease_id": "",
            "renewable": False,
            "lease_duration": 0,
            "data": {
                "data": {
                    "conn_type": "postgresql",