refactor: [SDK-5156] answer flag lookups instead of gating events

Follows KMP 31a7759: each event carries its own gate policy, so the host
only implements IFeatureFlagReader, "is this flag on", and CoreModule wires
that to IFeatureManager. Pins the submodule to the policy change.

Author: nan-li

OneSignal-KMP-SDK

@@ -114,7 +114,7 @@ internal class CoreModule : IModule {
         builder.register { provider ->
             val featureManager = provider.getService(IFeatureManager::class.java)
             LoggerFactory.createObservabilityEventRecorder(
-                gate = { event -> featureManager.isEnabled(event.flag) },
+                flags = { flag -> featureManager.isEnabled(flag) },
                 logger = AndroidLogger(),
             )
         }.provides<IObservabilityEventRecorder>()