Move AssetsProvider to native layer

Querying in the native layer for assets provided through
AssetsProviders does not currently work. This change refactors the
AssetProvider API to return a file descriptor that is read in the
native layer and can bubble up to the java layer.

This change also removes the InputStream API to favor of developers
using memfd_create.

Bug: 142716192
Test: atest ResourceLoaderValuesTest
Change-Id: I1a7eca0994c3b7cc32008d9a72bf91086ff0e816