Simplifying some launcher themes

> Replacing some colors with theme attributes
> Simplifying styles definition by removing unnecessary inheritance and inlining some definitions

Change-Id: Ifa167515cae6a7fd3720f1a52ff9ce11abb4495f

src/com/android/launcher3/allapps/AllAppsContainerView.java

@@ -464,10 +464,6 @@ public class AllAppsContainerView extends BaseContainerView implements DragSourc
             setLayoutParams(mlp);
         } else {
             View navBarBg = findViewById(R.id.nav_bar_bg);
-            if (Utilities.isAtLeastO()) {
-                navBarBg.setBackgroundColor(getResources().getColor(
-                        R.color.all_apps_light_navbar_color));
-            }
             ViewGroup.LayoutParams navBarBgLp = navBarBg.getLayoutParams();
             navBarBgLp.height = insets.bottom;
             navBarBg.setLayoutParams(navBarBgLp);