Remove remaining items from second_elapsed_callback and run_scheduled_events.

In #25375 (moved) we removed a bunch of stuff from these once-a-second functions, to the point where it's safe to disable them when the net is off.

Still, though, it would be cool to remove even more stuff, since we have better mechanisms to handle most of these, and since it would help us use less CPU in the non-disablenetwork case.