**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}`

for line in iter(process.stdout.readline, b""):
                        self.log.info(line.decode(self.output_encoding).rstrip())
                process.wait()
                if process.returncode:
                    raise AirflowException(f"Transform script failed: {process.returncode}")
            self.log.info("Transformation succeeded. Output temporarily located at %s", destination_file.name)
            self.log.info("Uploading file to %s as %s", self.destination_bucket, self.destination_object)
            FileDetailsLink.persist(
                context=context,
                task_instance=self,
                uri=f"{self.destination_bucket}/{self.destination_object}",
                project_id=hook.project_id,
            )
            hook.upload(
                bucket_name=self.destination_bucket,
                object_name=self.destination_object,
                filename=destination_file.name,
            )
class GCSTimeSpanFileTransformOperator(GoogleCloudBaseOperator):
    """
    Determines a list of objects that were added or modified at a GCS source
    location during a specific time-span, copies them to a temporary location
    on the local file system, runs a transform on this file as specified by
    the transformation script and uploads the output to the destination bucket.
    .. seealso::
        For more information on how to use this operator, take a look at the guide:
        :ref:`howto/operator:GCSTimeSpanFileTransformOperator`
    The locations of the source and the destination files in the local
    filesystem is provided as an first and second arguments to the
    transformation script. The time-span is passed to the transform script as