Stop using TIME_TICK broadcast in TextClock

This gets called even when the view is not visible, which is bad for
performance. I've adapted the existing tick framework to handle ticking
for minutes when there aren't seconds in the format.

I verified the correct behavior with sample apps with and without
seconds in the format, including across DST time changes.

Fix: 190467448
Test: locally with sample apps
Change-Id: I75fed5c9d162b5361c31fe22d057a007db0ce75c