[CustomHandler]Ensure HttpOutputBinding response is valid JSON #6644

• Throw error if output is not a JObject (to match the behavior with other out of proc behaviors today).

• Body of the output should be handled as a dynamic object so that no implicit .net type conversions happen during serialization and deserialization.

Above behavior specifically affects the ProcessDefaultInvocation codepath.

cc: Anthony Chu (@anthonychu) Pragna Gopa (@pragnagopa)