Don't set next_run when a zone is suspended

[dknowles2]

This is one of the problems with home-assistant/core#110054

If a zone is suspended, the time attribute returned is a constant of 50 years. This means that every time we refreshed the data, we got a moving value for the next run based on the delta from the current time at data refresh.

Instead of doing this, we just set next_run to None to indicate that we don't know when the next run will occur.

To fix a similar issue, we also clear out the microsecond value of the now datetime to make sure we don't drift slightly since the API only returns second-precision times.

Lastly, since we don't know the absolute time at which the suspension will end, we instead just set suspended_until to datetime.max, which also prevents date drifts from happening.