[jnigen] Include superinterface methods

[HosseinYousefi]

Closes #577.

• Adds the ability to clone various Elements in different stages of the code generation. Since the properties of the AST are added in multiple steps, the clone method gets an enum GenerationStage until and fills the values that are available until that stage.
• Copies the methods from the super-interfaces to the class.
• For generics like Foo<T>, Bar implements Foo<String> should have the methods of Foo, however all of the instances of T would have to be converted to String. _MethodMover in linker.dart handles this part.
• Merged Descriptor into Linker since we need it to distinguish between duplicate methods.
  • Technically the bytecode parser already has the descriptors, this is only a problem in the source parser where we generate the method descriptors in JNIgen.

[github-actions]

PR Health

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
jni	None	0.14.0	0.14.1-wip	0.14.0	✔️

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API leaks ⚠️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

Package	Leaked API symbols
jni	_opaque_pthread_mutex_t _opaque_pthread_cond_t _Dart_FinalizableHandle _ReferenceType

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License Headers ✔️

// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

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Files
pkgs/jni/lib/src/third_party/generated_bindings.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

[coveralls]

coverage: 81.519% (-0.006%) from 81.525%
when pulling 9e82b25 on include-methods-interfaces
into 2bc6d8d on main.

[HosseinYousefi]

Added a mixin on the top-level visitors, so the wrapper function only gets the visitor and checks if the stage is exactly previous stage + 1.

mixin TopLevelVisitor<R> on Visitor<Classes, R> {
  GenerationStage get stage;
}