Adding a copy constructor for RemoteViews

Copying a remoteView will not longer mutate the original views

Simplifying bitmap cache and memory measurement for remoteViews. A
remoteView tree will have a common bitmapCache, and hence ite memory
estimate would be same as the total bytes allocated to all the bitmaps.

Bug: 62629395
Test: am instrument -w -e class android.widget.RemoteViewsTest com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner
Change-Id: I7ea6ce476f19f425431ed01ef22cc97764626230