Add ResourcesProvider.loadFromDirectory

This API allows a directory to be loaded as if it was a zipped APK.
This is a substitute for the DirectoryAssetProvider API that
currently does not work in the native layer.

Bug: 142716192
Test: atest FrameworksResourceLoaderTests
Change-Id: Ia13e15653e75b421423dd56f9fe89e183ab4cb9a