Add dream descriptions to dream settings UI.

The dream descriptions will now be shown underneath the title, if the
dream has provided one.

We also cleaned up the icon view, instead merging it with the title view
to ensure proper alignment between the icon and title.

Bug: 221078654
Test: locally on device
Test: atest DreamPickerControllerTest
Change-Id: I00fd69c294f1a5fbcbc5392eba342f2896f6d9ed

src/com/android/settings/dream/DreamPickerController.java

@@ -111,6 +111,11 @@ public class DreamPickerController extends BasePreferenceController {
             return mDreamInfo.caption;
         }
 
+        @Override
+        public CharSequence getSummary() {
+            return mDreamInfo.description;
+        }
+
         @Override
         public Drawable getIcon() {
             return mDreamInfo.icon;