uninstall method
Called when this plugin is uninstalled, before scope is torn down.
Use this only for cleanup the registry cannot do automatically —
e.g. deregistering from singletons living outside scope, closing
external resources not held as services.
ServiceMixin services registered via registerAndInitService already
have dispose() cascaded via the standard unregister hook, so most
plugins do not need to override this.
Implementation
@visibleForOverriding
Resolvable<Unit> uninstall(DI scope) => syncUnit();