Improve image upload time estimation in OMERO.insight (see #10935)

This PR aims to improve the estimation of remaining upload time (and handling of MIFs therein). Some minor corrections might still be needed, as some of the code calling ``ImportLibrary`` is spread around and copied-and-pasted...

To test - try uploading an image big enough so that it is slow on a LAN (or upload from an ADSL connection) and see if the reported times make sense and give the user valuable feedback. Please check a MIF too.