Handle hidden RT VectorDrawable animators

This CL changes the target of VD specific animators to VectorDrawable,
instead of RenderNode. The benefit of doing so is that animators can
now detect whether the animation is meaningful by checking whether
their VD target is in the display list. If not, that means the VD is
not drawing for the current frame, in which case we can be smarter
and more power efficient by removing the animator from the list and
posting a delayed onFinished listener callback.

By setting VD as the animation target, when an ImageView decides to
update its drawable from one AVD to something else, we'll be able
to detect that the previous AVD is no longer in the display list,
and stop providing animation pulse to the stale AVD, which is
something we couldn't do previously.  This change also
handles the case where one AVD instance could be drawn in two
different views.

Bug: 27441375
Change-Id: Id4b3b37f28274c917cb9beb9dcd3d1e6991b5c5d