androidfw: Load SDK resources after initial system resources

* The existing AssetManager logic assumes a single system resource,
  as the RRO resource codepath expects to have the system AssetManager
  discover RRO overlay resources while the system resource is being
  added to the AssetManager's mAssetPaths. Having multiple system
  resources already present in the AssetManager's mAssetPaths breaks
  the expected ordering between the system AssetManager and the
  non-system AssetManager, as non-system AssetManagers will not need
  to discover system RRO overlay resources, and already have them
  in the it's mAssetPaths immediately following the system resource
  it is supposed to overlay.
* Resolve this issue by loading the SDK resources after the system
  RRO overlay resource is loaded to guarantee consistent ordering
  between the system AssetManager and non-system AssetManager instances.

Change-Id: I274cf9100fbb6215b840617993a7a6d9b7ff336d