Update linter config and address lint warnings/failures #2421

Job	Run time
Unit Test (knative/serving)	9m 47s
Unit Test (knative/networking)	4m 7s
Unit Test (knative/eventing)	13m 32s
Unit Test (knative/operator)	6m 43s
Unit Test (knative/client)	6m 51s
Unit Test (knative-extensions/eventing-autoscaler-keda)	4m 49s
Unit Test (knative-extensions/eventing-ceph)	4m 40s
Unit Test (knative-extensions/eventing-github)	5m 26s
Unit Test (knative-extensions/eventing-gitlab)	4m 54s
Unit Test (knative-extensions/eventing-kafka-broker)	11m 15s
Unit Test (knative-extensions/eventing-rabbitmq)	10m 17s
Unit Test (knative-extensions/eventing-redis)	5m 56s
Unit Test (knative-extensions/kn-plugin-admin)	4m 30s
Unit Test (knative-extensions/net-certmanager)	4m 24s
Unit Test (knative-extensions/net-contour)	4m 33s
Unit Test (knative-extensions/net-istio)	6m 1s
Unit Test (knative-extensions/net-kourier)	4m 26s
	1h 52m 11s

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