Change download and Install ETA to total time, not single file.

Currently, the Qt Maintenance tool shows a download and progress indication. There is a simple view, and the user can chose to expand to see more details about the progress.

However, we are still only showing the overall progress indication, and the download ETA of each single file. We should show the ETA of the total download in the simple view.

When the view is expanded we can also add the ETA of each single file, but most people care about the total much more!