The backup files are not compressed while using dumpling to GCS

[SE-Bin]

Feature Request

Is your feature request related to a problem? Please describe:

While using dumpling to back up the data of the TiDB cluster in Kubernetes to GCS. The backup data will be shrunk into a tgz file to upload. The TiDB cloud can not use this file to import data directly.

Describe the feature you'd like:

I can choose whether the backup data be compressed to upload to GCS while using the dumpling to backup the TiDB cluster in Kubernetes.

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

The user who wants to back up the data of TiDB Cluster in Kubernetes and with data migration to TiDB Cloud.

[sunzhaoyang]

Tools support GCS now.

So maybe the operator can deprecated the current implement (compress + rclone)