make pingsource adapter controller read-only

[lionelvillard]

Fixes #4028

Proposed Changes

• The adapter controller does not attempt to update the CR status
• Revert to previous behavior when the source is not ready. When a pod is deleted, a source becomes temporarily not ready, leading to lost events.

Release Note

Docs

[lionelvillard]

/cc @cr22rc

[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/adapter/mtping/controller.go	87.5%	88.9%	1.4
pkg/adapter/mtping/pingsource.go	71.4%	83.3%	11.9

[aliok]

/approve

Leaving lgtm to @cr22rc

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aliok, lionelvillard

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• OWNERS [lionelvillard]

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[knative-test-reporter-robot]

The following jobs failed:

Test name	Triggers	Retries
pull-knative-eventing-conformance-tests		0/3

Failed non-flaky tests preventing automatic retry of pull-knative-eventing-conformance-tests:

test/conformance.TestBrokerV1Beta1DataPlaneConsumer/MTChannelBasedBroker-eventing.knative.dev/v1beta1/Events_are_filtered
test/conformance.TestBrokerV1Beta1DataPlaneConsumer/MTChannelBasedBroker-eventing.knative.dev/v1beta1
test/conformance.TestBrokerV1Beta1DataPlaneConsumer
.Test

[lionelvillard]

/test pull-knative-eventing-conformance-tests

[cr22rc]

/lgtm