chore(datastore): added unit tests for Amplify Api Native Bridge (#4983)

* chore(datastore): added unit tests for Amplify Api Native Bridge

Unit tests for Query, Mutate, Subscribe, and Unsubscribe

* chore(datastore): updated Amplify Api Native Bridge unit tests per feedback

* chore(datastore): Formatted file

Author: tyllark

packages/amplify_datastore/lib/amplify_datastore.dart

@@ -110,7 +110,7 @@ class AmplifyDataStore extends DataStorePluginInterface
       config.api?.awsPlugin?.all.entries.forEach((e) {
         endpoints[e.key] = e.value.authorizationType.name;
       });
-      final nativePlugin = _NativeAmplifyApi(authProviders);
+      final nativePlugin = NativeAmplifyApi(authProviders);
       NativeApiPlugin.setup(nativePlugin);
 
       final nativeBridge = NativeApiBridge();
@@ -292,10 +292,11 @@ class _NativeAmplifyAuthCognito
   String get runtimeTypeName => '_NativeAmplifyAuthCognito';
 }
 
-class _NativeAmplifyApi
+@visibleForTesting
+class NativeAmplifyApi
     with AWSDebuggable, AmplifyLoggerMixin
     implements NativeApiPlugin {
-  _NativeAmplifyApi(this._authProviders);
+  NativeAmplifyApi(this._authProviders);
 
   /// The registered [APIAuthProvider] instances.
   final Map<APIAuthorizationType<AmplifyAuthProvider>, APIAuthProvider>
@@ -305,7 +306,7 @@ class _NativeAmplifyApi
       _subscriptionsCache = {};
 
   @override
-  String get runtimeTypeName => '_NativeAmplifyApi';
+  String get runtimeTypeName => 'NativeAmplifyApi';
 
   @override
   Future<String?> getLatestAuthToken(String providerName) {