### 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_get_scopes.return_value = ["scope1", "scope2"]
        mock_get_credentials.return_value = ("credentials", "project_id")
        vault_client = _VaultClient(
            auth_type="gcp",
            gcp_key_path="path.json",
            gcp_scopes="scope1,scope2",
            url="http://localhost:8180",
            auth_mount_point="other",
        )
        client = vault_client.client
        mock_hvac.Client.assert_called_with(url="http://localhost:8180")
        mock_get_scopes.assert_called_with("scope1,scope2")
        mock_get_credentials.assert_called_with(
            key_path="path.json", keyfile_dict=None, scopes=["scope1", "scope2"]
        )
        mock_hvac.Client.assert_called_with(url="http://localhost:8180")
        client.auth.gcp.configure.assert_called_with(credentials="credentials", mount_point="other")
        client.is_authenticated.assert_called_with()
        assert 2 == vault_client.kv_engine_version
    @mock.patch("airflow.providers.google.cloud.utils.credentials_provider._get_scopes")
    @mock.patch("airflow.providers.google.cloud.utils.credentials_provider.get_credentials_and_project_id")
    @mock.patch("airflow.providers.hashicorp._internal_client.vault_client.hvac")
    def test_gcp_dict(self, mock_hvac, mock_get_credentials, mock_get_scopes):