uv3 set-sorted index mishandles freespace in some cases

Testing with Ruta found a bug in the handling of free space in OrderedFsSet_array handling of freespace, when the freespace is moved down to the beginning of already present freespace. The amount of freespace added needs to account for already present freespace at the beginning.

Also fix toString to not processBatch - causes difficulties in debugging in this area (because the debugger calls toString if the GUI is showing this element).