**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}`

)
            == "prefix_with_year_month_day_and_percent_%/2015/02/01/"
        )
class TestGCSTimeSpanFileTransformOperator:
    @mock.patch("airflow.providers.google.cloud.operators.gcs.TemporaryDirectory")
    @mock.patch("airflow.providers.google.cloud.operators.gcs.subprocess")
    @mock.patch("airflow.providers.google.cloud.operators.gcs.GCSHook")
    def test_execute(self, mock_hook, mock_subprocess, mock_tempdir):
        source_bucket = TEST_BUCKET
        source_prefix = "source_prefix"
        source_gcp_conn_id = ""
        destination_bucket = TEST_BUCKET + "_dest"
        destination_prefix = "destination_prefix"
        destination_gcp_conn_id = ""
        transform_script = "script.py"
        source = "source"
        destination = "destination"
        file1 = "file1"
        file2 = "file2"
        timespan_start = datetime(2015, 2, 1, 15, 16, 17, 345, tzinfo=timezone.utc)
        timespan_end = timespan_start + timedelta(hours=1)
        mock_dag = mock.Mock()
        mock_dag.following_schedule = lambda x: x + timedelta(hours=1)
        mock_ti = mock.Mock()
        context = dict(
            execution_date=timespan_start,
            dag=mock_dag,
            ti=mock_ti,
        )
        mock_tempdir.return_value.__enter__.side_effect = [source, destination]