Conformance tests for channel status requirements

[aliok]

Problem

Following tasks are created according to the spec.

Tests:

• v1alpha1: When the channel instance is ready to receive events status.address.hostname and status.address.url MUST be populated and status.addressable MUST be set to True.
• v1beta1: When the channel instance is ready to receive events status.address.url MUST be populated and status.addressable MUST be set to True.

Note: As there's no way of knowing what channel spec version the channel supports, instantiate a channel and then check the annotation messaging.knative.dev/subscribable in the channel instance . There's more info for this in #2987.

Persona:
System Integrator, Contributors

Exit Criteria
Test required behavior of channel, maybe report on optional capabilities.

Time Estimate (optional):
1d

[aliok]

/area channels
/area test-and-release

[aliok]

/assign @aliok