Create dependency-proxy bucket when setup object storage

What does this merge request do and why?

This MR modifies object-storage-setup command to create dependency-proxy bucket.

How to set up and validate locally

The following guide expects that minio/data directory doesn't contain dependency-proxy directory.

In case it's already there and doesn't contain objects you would like to keep, than please delete it before.

$ make object-storage-setup
$ cd minio/data

Verify that dependency-proxy exists.

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.