Combine all exported parts of project in one tarball before serving it to the exporter user

Once all partial exports are complete as part of #360684 (closed) we need to be able to combine all the partially exported types of data into one tarball before serving it back to the user.

Diagram

sequenceDiagram
    autonumber

    participant export_service as Projects#58;#58;ImportExport#58;#58;ExportService
    participant relations_worker as Projects#58;#58;ImportExport#58;#58;RelationExportWorker
    participant tracker as Project#58;#58;ImportExport#58;#58;TrackExportRelationsWorker
    participant export_worker as ProjectExportWorker
    participant export_service as Projects#58;#58;ImportExport#58;#58;ExportService
    participant after_export_worker as Projects#58;#58;ImportExport#58;#58;AfterExportWorker

    par Generate relations in parallel
        export_service->>relations_worker: Enqueue worker to generate relation A
        export_service->>relations_worker: Enqueue worker to generate relation B
        export_service->>relations_worker: Enqueue worker to generate relation C
        export_service->>relations_worker: ...
    end

    export_service->>tracker: Enqueues TrackerExportRelationsWorker
    loop
        tracker->>tracker: Monitor if all relations were generated. <br />Keep re-enqueing itself until all relations are generated.<br />Notify user in case of an error occurs
    end
 
    tracker->>export_worker: Enqueue worker 
    Note right of export_worker: Download exported relations<br />and create tarball
    export_worker->>after_export_worker: Enqueue worker 
    Note right of after_export_worker: Send the file to S3, email user, etc

Technical details

In this issue, we will implement the code needed for step 8 of the diagram above: download, decompress, and combine all partial export relations into a single tarball with the same structure as the export file currently generated.

After creating the final tarball, we will upload it to the object store similarly to how it is done in ProjectExportWorker.