Meta `Channel` doesn't conform the spec's status subscribers requirement

[aliok]

Describe the bug
As noted in #3016 (comment), Channel doesn't have subscribers in the status.

That PR is about adding conformance tests for channels around having subscribers array in the status.

Spec says this:

• v1alpha1
  Each subscription to a channel is added to the channel
  status.subscribableStatus.subscribers automatically. The ready field of the
  subscriber identified by its uid MUST be set to True when the subscription
  is ready to be processed.
• v1beta1
  Each subscription to a channel is added to the channel status.subscribers
  automatically. The ready field of the subscriber identified by its uid MUST
  be set to True when the subscription is ready to be processed.

When a channel.messaging.knative.dev is created, by default Knative creates an InMemoryChannel. When we create a subscription against that Channel, InMemoryChannel will have the subscribers in the status, but it is not propagated to channel.messaging.knative.dev. Other fields like status.address are propagated fine.

Expected behavior
channel.messaging.knative.dev should have status.subscribers and #3016 should pass.

To Reproduce

• Create a channel.messaging.knative.dev
• Create a subscription
• No status.subscribers nor status.subscribableStatus.subscribers is there.

See #3016

Knative release version
0.14

Additional context
#3016

[aliok]

/area channels
/area test-and-release

[aliok]

/project Channels

[knative-prow-robot]

@aliok: You must be a member of the knative/eventing github team to set the project and column.

Details

In response to this:

/project Channels

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[aliok]

Some info here: #3051 (comment)
That ticket is about the subscribers info in status, not in spec but it is also said that status should be propagated from the underlying channel to meta Channel

[aliok]

/close

Fixed by #3088

#3016 is now green