Add a strict mode for parsing responses

[lwasyl]

Original discussion on Kotlinlang Slack: https://kotlinlang.slack.com/archives/C01A6KM1SBZ/p1631193087025200

Such strict mode could check that the parsed responses contain exactly the data that schema and query describe:

• all __typename values match the types defined by the schema
• there are no additional fields/objects in the json response (excluding extensions)