**Description**

Support passing multiple prefixes to `GoogleCloudStorageListOperator` and `GoogleCloudStorageDeleteOperator` operators.

**Use case / motivation**

I have this folder structure in GCS bucket.

```
+-- year={year}
|   +-- month={month}
|       +--day={day}
|           +-- topic={topic1}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic2}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic3}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic4}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic5}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic6}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic7}
|       +--day={day}
|           +-- topic={topic1}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic2}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic3}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic4}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic5}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic6}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           +-- topic={topic7}
|                 +--file 1
|                 +--file 2
|                 +--file 3
|           ....
```

What I need to achieve is delete one day of objects. For example, I need to delete objects in `year=2020/month=08/day=19`. I can do that easily using `gsutils`. In `gsutil` you can delete them via wild card `gsutil ear=2020/month=08/day=19/*` but using the REST APIs you can't even if you use a prefix. The reason is there is no one prefix to get all the objects inside a folder. I achieved that by using multiple prefixes and for each prefix, I will get the list of objects. Unfortunately, I can't pass more than one prefix to the operators.

**Prefixes used**
- `year=2020/month=08/day=19/topic={topic1}`
- `year=2020/month=08/day=19/topic={topic2}`
- `year=2020/month=08/day=19/topic={topic3}`
- `year=2020/month=08/day=19/topic={topic4}`
- `year=2020/month=08/day=19/topic={topic5}`
- `year=2020/month=08/day=19/topic={topic6}`
- `year=2020/month=08/day=19/topic={topic7}`

test_bucket = "test_bucket"
        test_project = "test-project"
        test_location = "EU"
        test_labels = {"env": "prod"}
        test_storage_class = "MULTI_REGIONAL"
        labels_with_version = copy.deepcopy(test_labels)
        labels_with_version["airflow-version"] = "v" + version.replace(".", "-").replace("+", "-")
        mock_service.return_value.bucket.return_value.create.return_value = None
        mock_bucket.return_value.storage_class = test_storage_class
        mock_bucket.return_value.labels = labels_with_version
        sample_bucket = mock_service().bucket(bucket_name=test_bucket)
        response = self.gcs_hook.create_bucket(
            bucket_name=test_bucket,
            storage_class=test_storage_class,
            location=test_location,
            labels=test_labels,
            project_id=test_project,
        )
        assert response == sample_bucket.id
        assert sample_bucket.storage_class == test_storage_class
        assert sample_bucket.labels == test_labels
        mock_service.return_value.bucket.return_value.create.assert_called_once_with(
            project=test_project, location=test_location
        )
    @mock.patch("google.cloud.storage.Bucket")
    @mock.patch(GCS_STRING.format("GCSHook.get_conn"))
    def test_create_bucket_with_resource(self, mock_service, mock_bucket):