Delivery format: Support the `format` field on the subscription delivery spec for IMC

[Cali0707]

Problem To allow for specifying the cloudevent format when delivering events from a subscription to an imc, we should support the format field on the delivery spec of the subscription. Specifically we will need to:

1. Add the field to the CRD
2. Depending on the value of the field, correctly configure the kncloudevents dispatcher in the imc dispatcher component to send the cloudevent with the correct binding

Persona: Which persona is this feature for?

Exit Criteria An e2e test indicating that subscriptions deliver events with the correct format (structured, binary, input)

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: #8057