Show duration change at history tab

[dremdem]

Follow-up from #604

Quote from the original issue:

Add an duration for TC run as well. It'll also would be nice to add some traction arrows to Duration entry(arrows on the screenshot are for illustration only)

Rationale

We have group of tests that should run no longer then given threshold.
So, our daily routine to check the slowest tests from this group and it will nice to have the history
of the run duration of the certain test.

[baev]

Do you have any other ideas on what information/widgets/etc can help you with your problem?

[dremdem]

In general, we can start with the analysis of the Duration trend graph:

• if we discover some drastic rises in the duration, we need to know who the suspect is
• then we can go to the Behaviours tab, sort by duration and see the top N slowest

• and final step is to understand what is the duration trend of every slow test. That's why we need this feature that will show the duration of the exact test