Propagate density through AdaptiveIconDrawable and BitmapDrawable

Resources#getDrawableForDensity now propagates the overridden
density through to AdaptiveIconDrawable so that the density can be
propagated to leaf BitmapDrawables correctly.

This enables AdaptiveIconDrawable to support higher resolution
foreground/background bitmaps for use in Launcher.

Bug: 36039665
Test: bit CtsContentTestCases:android.content.res.cts.ResourcesTest
Change-Id: Iaa9a5592626e38e1ff839a76f7c6cfb9e16e5dc1