TMSS-2847: call evaluate_daily_constraints from get_earliest_possible_start_time_for_daily_constraints with non-gridded timestamp, in order to yield the correct non-gridded earliest_possible_start. Fixed blinking test_triggered_scheduling_unit_unschedules_regular_observation

TMSS-2847: evaluate_sky_min_elevation_constraint returned the incorrect earliest_start_time. Simplified it, and let it work together with get_earliest_possible_start_time_for_sky_min_elevationto better find the actual earliest_possible_start_time for sky_min_elevation