We already don't run instrumentation tests in CI,
so we should at least compile them to catch any breakage there.
This is important as they don't even get compliled when building and
installing the app with Android Studio.
* With Android.bp support merged in (and working well for both 10 and 11),
we keep that as the primary and supported method to integrate Seedvault.
* Gradle can still be used for development
* You can still use your own prebuilts if you want, we just won't be
putting them out ourselves
* to get rid of global state
* to have a testable architecture
* to allow for authenticated encryption
* to have a backup format version
* to potentially allow for other storage plugins
