[DO NOT MERGE] Pre-allocate height for contextual cards.

To prevent the UI jank causing by the async card loads, we pre-allocate
some space for the card to fill in. After this change, only one card can
be shown at a time.

More details:
- When the card number configuration is set to 0, don't trigger the card
loader.
- The height adjusting logic is as follows.
When Settings is opened, pre-allocate a space first.
After the RV finish laying out, reset the RV to wrap_content. So if the
card has to be expanded(eg. wifi large mode or dismissal view), then it
will adjust the height accordingly. While if a card previously shown
becomes unavailable(dismissed or conditions not meet), we also reset the
RV so the space can be gone.

Bug: 163288869
Test: robotest
Change-Id: I0dcb2dae8f0533e562ad06f664b7ae7a9afecd21

src/com/android/settings/homepage/contextualcards/ContextualCardManager.java

@@ -122,6 +122,10 @@ public class ContextualCardManager implements ContextualCardLoader.CardContentLo
             Log.w(TAG, "Legacy suggestion contextual card enabled, skipping contextual cards.");
             return;
         }
+        if (ContextualCardLoader.getCardCount(mContext) <= 0) {
+            Log.w(TAG, "Card count is zero, skipping contextual cards.");
+            return;
+        }
         mStartTime = System.currentTimeMillis();
         final CardContentLoaderCallbacks cardContentLoaderCallbacks =
                 new CardContentLoaderCallbacks(mContext);