NuPlayer: adjust temporal-layers to achieve smooth play

For multi-layer-encoded content (with hierarchical referencing),
select a subset of layers based on playback speed.

Bug: 27596987
Change-Id: I824c699f3c2b80bb516c1b44493eda72239291ac
(cherry picked from commit 64ad0e0b2b5f992052d287e82ebd79f9f892dcbf)