Support displaying repositories which are currently in progress when paginating

In order to support our pagination efforts in #222889 (closed) we need a way to gather information about repositories currently being imported.

Previously this information was provided within status.json response. It needs to be moved out so status.json will report only paginated data

Also frontend needs to be updated to load data from separate endpoint and display it independently of current page

Availability & Testing

• Update gitlab-org/quality/testcases#1762 (closed) if necessary
• Trigger package-and-qa job to see if existing e2e tests pass