Improved app config handling (Identifier, local fallback) (DEV) (#1553)

* Add default app config as last resort fallback.

* Change config type names and improve logging for HotDataFlow.kt

* Run the app config retrieval on the app scope, otherwise UI unsubscription could cancel the app config retrieval.

* Offer "identifier" property that can identify app configs such that subscribers know when it is considered changed.

* Behavior change AppConfigProvider.kt, there is no caching/replay grace period, once the last subscription is gone, it's  last value is cleared.

* Klint ;)

* Add a unit test specifically for checking the default configs checkum and parsability.

* Fix test breaking on CI.

* Don't check the checksum for the config loaded from assets.

Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>