Add E2E test case to test Provisioner/Channel's persistence feature

[chizhg]

Problem
A couple of Provisioner/Channel implementations support persistence, like GCP PubSub. We need E2E test case to verify this feature.

Exit Criteria
An E2E test case is added to verify the persistence feature for channels that support it.

[vaikas]

@Fredy-Z is this something that might be worked on as part of the Channel Task Force.
@Harwayne
@matzew

[slinkydeveloper]

I think this is something @pierDipi solved, right? Now we have retry tests for brokers

[pierDipi]

We have redelivery tests for brokers, however, IMO testing persistency is a bit different because a channel can retry in memory and never persist events.

I didn't see any reference to the persistence feature in the spec, do we really want this to be a conformance test? (inferred from the label area/conformance)

[slinkydeveloper]

Yes this is probably something that was thought in the past and never really spec-ed, implemented. The persistence exists in our channel/broker implementations, apart from imc, but there is no spec feature to describe. I think we can close it, reopen if you need it

/close

[knative-prow-robot]

@slinkydeveloper: Closing this issue.

Details

In response to this:

Yes this is probably something that was thought in the past and never really spec-ed, implemented. I think we can close it, reopen if you need it

/close

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