Add start margin in the Screen usage item

Avoid the title and subtitle overlap while text length is long. So add the
start margin for subtitle.

Fixes: 136282569
Test: manual test
Change-Id: Id1728ae60904c654c4ffe95fae7fb5139f368092

res/layout/preference_widget_summary.xml

@@ -18,6 +18,7 @@
     android:id="@+id/widget_summary"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
+    android:layout_marginStart="8dp"
     android:drawablePadding="8dp"
     android:gravity="center_vertical|end"
     android:textAlignment="viewEnd"