Add test duration field per test in session view

[joeshakked]

Before the latest makeover, the old UI included a "duration' field along side the start-end time for each tests in the session view tests list.
I think it was useful and should be re-added

[vmalloc]

Sure, I will add it back. However I don't think it would fit on smaller screens (it was dropped following many width issues with long test names and/or subject names)