Document all the different resource kinds

[saturnism]

Is this a BUG or FEATURE REQUEST?: Feature Request

Did you review https://istio.io/help/ and existing issues to identify if this is already solved or being worked on?: Yes

Bug: No

What Version of Istio and Kubernetes are you using, where did you get Istio from, Installation details N/A

Is Istio Auth enabled or not ? N/A

What happened: When looking at a Circuit Breaker configuration it's impossible to tell what the resource kind should be (e.g., DestinationPolicy).

What you expected to happen: Document all the high-level kinds and their hierarchy.

How to reproduce it: See https://istio.io/docs/reference/config/istio.routing.v1alpha1.html#CircuitBreaker

Feature Request: Y