Excluding trailing spaces from the content size means the cursor
position also needs to considered in determining the width used
by the text as unwrapped white space can push the cursor over
the width of the item.

Also corrects an auto scroll issue with right to left text
identified in extending the tests.

Task-number: QTBUG-24630

Change-Id: Iaab9eac03824b22f507154fa1d6e55376bd075a0
Reviewed-by: Yann Bodson <yann.bodson@nokia.com>