Tell PhoneWindowManager when we start/finish interactive changes.

Added some new callbacks that can be used to more precisely trigger
certain behaviors that need to happen around the time the device
is put to sleep and locked.

Fixed an issue where the going to sleep signal might be sent too
early on devices that don't support ambient mode due to the extra
wakefulness change between DOZING and ASLEEP.  We are now track
the early / late interactive change work separately from the rest.

Bug: 21375811
Change-Id: I95387195e216ae92a6e45485bd1bd362e41aa45a