Fix ROI resizing in Insight (see #11384)

This PR fixes https://trac.openmicroscopy.org.uk/ome/ticket/11384 and also add a bonus feature. 

Now a checkbox with the "Scale Proportionally" is present in the Inspector tab of the Measurement Tool (ROI) in Insight. As expected, when the checkbox is checked, the ROI will be set to a new size with both width and height updated with the same value.

To test this PR:
- make sure that the behaviour from https://trac.openmicroscopy.org.uk/ome/ticket/11384 doesn't happen anymore,
- verify that the new checkbox works and changes behaviour as expected.

This PR will most probably be have to rebased onto ``develop``.