Function embedder_traits::resources::resources_for_tests

fn resources_for_tests() -> Box<dyn ResourceReaderMethods + Sync + Send>

Bake all of our resources into this crate for tests, unless we are cfg!(servo_production).

Local non-production embedder builds (e.g. servoshell) can still override these with set, if runtime loading of prefs.json and other resources is needed. On OpenHarmony we never want to include files, since we ship all the files in the application bundle anyway.