Delivery format: dispatch events in format specifed by EgressConfig

[Cali0707]

Problem
In #3970 we are adding a field to the EgressCongfig to detail the format events should be dispatched in. The dispatcher needs to be updated to send the evens in that format to the subscriber.

Persona:
Which persona is this feature for?

Exit Criteria
Unit tests that the dataplane dispatchers are sending events in the correct format

Time Estimate (optional):
How many developer-days do you think this may take to resolve? 1-2

Additional context (optional)
Add any other context about the feature request here.

• Parent issue: Delivery Format: support specifying the event format knative/eventing#8057

[Cali0707]

/help
/triage accepted

[knative-prow]

@Cali0707:
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In response to this:

/help
/triage accepted

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