Express Tap/Target settings as JSON schema within Singer YAML

To match what will be generated by the SDK, the settings in a tap/target definition should be expressed as JSON schema https://gitlab.com/meltano/singer-sdk/-/blob/main/singer_sdk/helpers/_typing.py

In handling this, better define the kinds and think about how password is perhaps not the best way to describe it. This is tracked in #25 (closed)

I've validated that we can dump JSON Schema into YAML 🙂