efl_ui_spec: add a test suite for the steady event
this checks that the steady event is correctly emitted after some time.
Right now this test does notthing for EFL_UI_SPIN_CLASS. Reason for this
is that Spin is not interactive, even if it implements the interface for
it. Maybe something we should resolve in future.
Reviewed-by: Mike Blumenkrantz <firstname.lastname@example.org>
Differential Revision: https://phab.enlightenment.org/D9460