Add detailed messaging about in-progress GitLab direct transfer

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Currently whenever a user uses GitLab direct transfer, they don't have much visibility into the migration itself. They do see which groups/projects are 'in progress' and see any failures that occurred, but there's no visibility into the following cases:

• When migration is waiting for export to finish exporting data. This is particularly useful when the migration is 'stuck' waiting for source gitlab to complete export
• Which type of relation is 'currently' importing
• Which stage (out of how many) is currently running

It would be good to add this information so user can understand where the overall migration is at.