Improve order of rows in a classification report with all taxa sorted by the number of reads

If one selects "All taxa"="True" and "Sort by"="Number of reads" in the classification report element (see UGENE-6088), rows with zero number of reads are not sorted at all.

Modify it so that rows are output as follows:

• Rows with non-zero number of reads (sorted by this number).
• The remaining rows with zero number of reads, sorted by taxID.