Json deserialization of AdaptiveRichTextBlock fails

Platform

• .NET

Version of SDK

latest (NuGet 3.0.0)

Issue

When I deserialize an AdaptiveRichTextBlock from Json the Inlines attribute is expected to by a Json array but the serializer creates an object.
I observed this in Botframework v4 when using an AdaptiveRichTextBlock in a prompt. When the user sends a response to the prompt the Botframework is unable to restore the context due to this issue.

Steps to Reproduce

using AdaptiveCards;
using Newtonsoft.Json;

var s = JsonConvert.SerializeObject(new AdaptiveRichTextBlock
{
  Inlines = new List<AdaptiveInline>
  {
    new AdaptiveTextRun
    {
      Text = "test"
    }
  }
}, new JsonSerializerSettings { TypeNameHandling = TypeNameHandling.All });
var o = JsonConvert.DeserializeObject<AdaptiveRichTextBlock>(s);

The AdaptiveRichTextBlock is serialized to

{
  "$type": "AdaptiveCards.AdaptiveRichTextBlock, AdaptiveCards",
  "type": "RichTextBlock",
  "inlines": {
    "$type": "System.Collections.Generic.List`1[[AdaptiveCards.AdaptiveInline, AdaptiveCards]], System.Private.CoreLib",
    "$values": [
      {
        "$type": "AdaptiveCards.AdaptiveTextRun, AdaptiveCards",
        "type": "TextRun",
        "text": "test"
      }
    ]
  }
}

but the deserializer expects

{
  "$type": "AdaptiveCards.AdaptiveRichTextBlock, AdaptiveCards",
  "type": "RichTextBlock",
  "inlines": [
    {
      "$type": "AdaptiveCards.AdaptiveTextRun, AdaptiveCards",
      "type": "TextRun",
      "text": "test"
    }
  ]
}

Start by running the provided C# reproduction with AdaptiveRichTextBlock, Newtonsoft.Json, and TypeNameHandling.All. Inspect the AdaptiveRichTextBlock serialization and deserialization path; done means the round trip succeeds and produces the expected inlines array shape without breaking polymorphic inline types.