Improve transparent bar transitions.

1. Migrate transparent transitions to the new optimized
background color animations.

2. Ensure sysui animation transparent -> opaque has enough
time to run before window manager crops off the content area.

3. Lose the individual alpha on each status bar icon if the bars
are not opaque.  Animate the alpha if visible, make sure they
play together.

4. Documentation typo fix found in AnimatorSet.

Bug:10344949
Change-Id: I615668ce3c552d3df15dbba5cdeeca67549a0220