**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}`

return b"x" * 393216
@pytest.fixture(scope="module")
def testdata_string(testdata_bytes):
    return testdata_bytes.decode()
@pytest.fixture(scope="module")
def testdata_file(request, tmp_path_factory, testdata_bytes):
    fn = tmp_path_factory.mktemp(request.node.name) / "testfile_data"
    fn.write_bytes(testdata_bytes)
    yield str(fn)
class TestGCSHookHelperFunctions:
    def test_parse_gcs_url(self):
        """
        Test GCS url parsing
        """
        assert gcs._parse_gcs_url("gs://bucket/path/to/blob") == ("bucket", "path/to/blob")
        
        with pytest.raises(AirflowException):
            gcs._parse_gcs_url("gs:/bucket/path/to/blob")
        with pytest.raises(AirflowException):
            gcs._parse_gcs_url("http://google.com/aaa")
        
        assert gcs._parse_gcs_url("gs://bucket/path/to/blob/") == ("bucket", "path/to/blob/")
        
        assert gcs._parse_gcs_url("gs://bucket/") == ("bucket", "")
class TestFallbackObjectUrlToObjectNameAndBucketName:
    def setup_method(self):
        self.assertion_on_body = mock.MagicMock()
        @_fallback_object_url_to_object_name_and_bucket_name()
        def test_method(_, bucket_name=None, object_name=None, object_url=None):