Project "Transfer Project" button in modal is clickable while transfer is in progress

Proposal

When in the Transfer Project modal window, the Confirm red confirmation button stays as an active button after the button has been clicked and the transfer process has started (and takes 20-60 seconds in some cases?). There is no indication to the user that the transfer has started, so it feels like the user is stuck or application has a bug.

Option 1: After clicked, the button state changes to grayed out with spinning wheel icon.

Option 2: Borrow the UI with a spinning progress wheel from Importing a Project (ex. from a GitLab Export).

Initial triage in Slack thread. During triage we did find a 500 error during import that is being tracked in a linked issue.

cc @acroitor