Adapt testing structure to run source conformance tests

[aliok]

Problem
Similar to brokers and channels, we need to provide what sources to run conformance tests against

Persona:
Which persona is this feature for?

Exit Criteria
System Integrator, Contributors

Time Estimate (optional):
1d

Additional context (optional)
See ChannelTestRunner in knative/eventing

/area sources
/area test-and-release

[devguyio]

/assign

[aliok]

/close

Fixed by #3340

[knative-prow-robot]

@aliok: Closing this issue.

Details

In response to this:

/close

Fixed by #3340

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