FR: be able to display only tests which remain to run

[ymeine]

For now, with filters it is possible to display only tests which:

• failed
• didn't run at all
• etc.

But we can't filter tests in order to display only those which still have to be executed, even if they've be run (unsuccessfully then) once (at least) already. Those tests are visually represented in the table with the failure icon but in a transparent fashion.

[divdavem]

It is now possible to display only tests which remain to run, by setting the Execution chooser parameter to Last instead of the default Last non-waiting, and filtering with the ? button (cf change in commit fae00e8)