Activity Completed Background Update

[JosephAbbey]

Aside from temporal events, the only useful trigger for background services is activity completion (https://developer.garmin.com/connect-iq/api-docs/Toybox/Background.html#registerForActivityCompletedEvent-instance_method).

Updating the states instantly on completion would allow for better automations:

• More reliable stop watch reminders.
• Trigger on completion.

We should be able to use the same callback that is already implemented for temporal events.

[philipabbey]

https://developer.garmin.com/connect-iq/api-docs/Toybox/System/ServiceDelegate.html#onActivityCompleted-instance_function

Have onActivityCompleted() call onTemporalEvent()?

• Factor out the code in onTemporalEvent() to allow for sport and subsport to be parameters.
• onActivityCompleted() supplies both parameters as -1 for end of activity.