Rename ZenRule.isAutomaticActive() to isActive()

The word "automatic" was a bit shaky already and is doubly wrong with MODES_UI:
* it also applies to the manual rule, not only automatic rules.
* it considers manual override / snoozing, on top of the automatic value.

Fixes: 363193376
Test: N/A, automatic refactor
Flag: EXEMPT automatic refactor
Change-Id: I96b168c89eae8dec8b1d535431324e44b1687a86