reconcile eventing with v1 resources, generate v1 dependent resources

[vaikas]

Fixes #3580

Proposed Changes

• Reconcile eventing.{Broker, Trigger} with v1 shape
• Generate / operate on dependent resources using v1 shapes (Subscriptions, channels, etc.)

Release Note

- 🧽 Update or clean up current behavior
Reconcile eventing.{Broker,Trigger} using v1 api shape. Operate on dependent resources (Subscriptions, etc.) using their v1 shapes.

Docs

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: vaikas

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[knative-metrics-robot]

The following is the coverage report on the affected files.
Say /test pull-knative-eventing-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/apis/duck/v1/register.go	Do not exist	100.0%

[nachocano]

/lgtm