Do not import top level library internally

Author: HosseinYousefi

pkgs/jni/lib/src/errors.dart

@@ -4,7 +4,8 @@
 
 import 'dart:io';
 
-import '../_internal.dart';
+import 'package:meta/meta.dart' show internal;
+
 import 'third_party/generated_bindings.dart';
 
 // TODO(#567): Add the fact that [JException] is now a [JObject] to the

pkgs/jni/lib/src/jimplementer.dart

@@ -7,10 +7,11 @@ import 'dart:isolate';
 
 import 'package:meta/meta.dart' show internal;
 
-import '../jni.dart';
 import 'accessors.dart';
 import 'jni.dart';
+import 'jobject.dart';
 import 'third_party/generated_bindings.dart';
+import 'types.dart';
 
 /// A builder that builds proxy objects that implement one or more interfaces.
 ///