Plug leaks in transitions

Transitions were leaking views due to TransitionsValues holding references
to views/parents. The references were fine, but the retention of the transition
objects themselves were not. There were a few different places that needed to
be plugged:
- clones were not making new copies of some fields, leading to caching references
in the original object (which was then cloned later to other clones)
- Visibility was using a persistent field to cache temporary values. This transition,
when cloned, would retain these instances, keeping references to views
- ViewTreeObserver had a bug that would leak listeners

Issue #10749071 Activity instance leak between TransitionManager and InputMethodManager

Change-Id: I1d5d457dc5e020c7b9e8392a95e3b2c488461119