Show a download button for export processes

https://redmine.teklia.com/issues/7497

Requires backend#1858 (closed), backend#1862 (closed), #1505 (closed)

For Export processes that are in a final state, the process list and status views should show a Download button that opens DownloadProcessArtifact in a new tab.

In the process list view, this should show as a has-text-primary button in the Actions column, similarly to the existing Retry button.

In the process status view, this should be the very first action in the Actions menu.