Evaluate replacing JsonConvert serialization

まず Installer の savedState がどのようにシリアライズおよびデシリアライズされるかを追跡し、次に issue で議論されている netstandard2.0 のシリアライザーオプション（NetDataContractSerializer と BinaryFormatter を含む）を比較します。任意の IDictionary と子 Installer の状態が Json.NET なしでラウンドトリップできるかを検証します。互換性のある置き換えを特定するか、依存関係を残す必要がある理由を文書化できれば完了です。

It looks like you're just using JSON.net to serialize IDictionary in savedState and this could be accomplished with built-in serializers that would remove the dependency on JSON.net (so that a different version can be used or just not bring that dependency along with someone using System.Configuration.Install).

I looked at the reference source and the built-in classes use NetDataContractSerializer which can serialize/deserialize arbitrary types in an IDictionary. We don't have that in netstandard2.0. Another possibility is BinaryFormatter, but that requires ISerializable which IDictionary is not. The concrete type is Hashtable in the underlying implementation for installers.

@flamencist thought this approach might work, but it relies on ToString() to put it in a key value store. Since IDictionary (and Hashtable) can hold any object, this doesn't really work. Some objects may not have a sensible ToString() which would end up with the type name in the output, and they can't really be deserialized in this manner.

In the Installer source I looked at, it appeared that it was putting an integer in there for the count of Installers and then saving all the child Installer states (which can be any object since anyone can inherit Installer).

The reason JsonConvert works is that it serializes the type information too. Is it possible to replace it with something we have in netstandard2.0 so that we don't have to bring along a JSON.Net dependency?