Add gitlab:packages:migrate task to migrate package files to object storage
What does this MR do?
What are the relevant issue numbers?
Does this MR meet the acceptance criteria?
- Changelog entry added, if necessary
- Documentation created/updated
- Tests added for this feature/bug
- Conforms to the code review guidelines
- Conforms to the merge request performance guidelines
- Conforms to the style guides
- Conforms to the database guides
EE specific content should be in the top level
- For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?