Add 'until next alarm' option to QS zen panel.

Unlike the implementation in LMR1, this is a countdown condition
(a countdown until the time of what was the next alarm when the
rule was created). The rule will not change if alarms change.
Also, alarms up to 7 days in the future will be considered.

Bug: 21648799
Change-Id: Id7fa9dbdbad1539e4da19b1d0e0c4395bb13e6cb