Make Serial number preference a copyable slice.

Fixes: 73769621
Test: robotests
Change-Id: Ic20d8865bc26c1acc7db74e665f92fe388d62f74

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

@@ -23,6 +23,7 @@ import static com.android.settings.slices.CustomSliceRegistry.NOTIFICATION_CHANN
 import android.content.Context;
 import android.database.ContentObserver;
 import android.database.Cursor;
+import android.net.Uri;
 import android.os.Handler;
 import android.os.Looper;
 import android.text.format.DateUtils;