Run the OpenHTF teardown when a run is stopped

Stopping an OpenHTF run from the operator UI, the terminal or a signal used to kill the test outright: no plug tearDown, no PhaseGroup teardown phase, and nothing uploaded.

• Added a clean stop for OpenHTF runs, the way OpenHTF stops on its own Ctrl-C: the running phase is interrupted, the PhaseGroup teardown phases and the plugs' tearDown run, and the run is uploaded as ABORTED with the phases that completed
• Added a Kill that matches OpenHTF's second Ctrl-C: the teardown phase under way is abandoned, the plugs are still released and the run is still uploaded, with a forced kill only when the process has not exited seven seconds later
• Fixed stopped runs being reported as FAIL on both frameworks: they now report ABORTED and exit with code 130, and a run the procedure stops itself exits with code 3
• Added the ui_cancelled event for agents when an open prompt is withdrawn with its interrupted phase