Leanback media-list support: Added optional customizable actions

AbstractMediaItemPresenter now supports arbitrary number of optional
custom actions. Each media item row can consist of multiple, separately
focusable views where each component is highlighted through an animated
drawable.

APIs are provided for capturing click events on media item details or
actions, and dynamically altering the contents of the details or
action views.

Also changed the attribute names to "media items" to make them more
generic for any media item list usage (e.g. music app, podcast, etc.).

Bug: 28636413
Change-Id: I167fc15c3961dec4280a77c1356f1bf571525650
16 files changed