WLED scheduled start and stop support

[ptr727]

Support WLED schedules with a dedicated start and stop time per schedule.

I run WLED schedules daily and on themed holidays.
WLED and overlay style events cannot be scheduled in the same way a sequence can, i.e. there is no stop time for WLED schedules.
This requires that the WLED start triggers needs to be scheduled, and a single stop trigger also be scheduled.
The lack of a stop per start trigger means that there is no ability to schedule independent start and stop times.
E.g. on most days I want lights of at 11pm, on new year I want lights of at 1am, and this is not possible unless I manually change the stop schedule.

I'd like to see WLED treated in a similar way as sequences, i.e. scheduled start and stop times per entry.

[cpinkham]

This functionality would depend on #1378 to be completed. Currently we do not have a way to keep track of what WLED effects are running. This logic would need to be added to complete #1378. Once we can keep track of running WLED effects, we could then update the stop command to allow stopping a specific effect and this stop command could be scheduled using the existing scheduler functionality. Closing this ticket and referencing #1378 connect the two tickets.