Deprecate optional Knative Eventing components from common manifests

[rawc0der]

Description:
There are certain components which get deployed alongside all the required core Kubeflow stack. One example is the knative-eventing which is installed together with the KNative stack of services.

• manifests/common/knative/knative-eventing-post-install-jobs/base
• manifests/common/knative/knative-eventing/base

Suggestion:
If this component is not required for Kubeflow inner workings, then my suggestion is to deprecate it from the /common folder. This install creates a lot of unnecessary deployments and resources on the cluster (which rarely get used for critical functionality).

Deprecation Note:
In order to keep the integration and still allow users to continue installing it if needed, it can be added as separate integration to /contrib folder.
If this introduce inconsistent conventions, then it could simply be commented out from the installation kustomization file such that it is not considered as required.

Any thoughts?