Add support for configForSplit

Applications with the android:isolatedSplits="true" attribute in
their AndroidManifest.xml would have their Split APKs loaded in
isolation of each other, based on a set of dependencies.

Configuration Splits generated for a Feature split would not be properly
loaded before, so this change, along with a tools change, fixes this
issue and completes support for isolatedSplits.

Bug: 30999713
Test: CTS test coming (depends on some tool changes)
Change-Id: Ia4e7b0e69168a9d6637867558e306f7031720fb3