Add a configuration for SecurityContext to reconciled eventlistener Deployment

[vdemeester]

With #862 is merged, eventlistener deployment are no more able to be created, by default on OpenShift.
The reason for it is that, by default, you cannot set uid for your Pods, OpenShift takes care of this. To be able to use runAsUser: 65532 on OpenShift, you need to use anyuid which is a higher privilege than you usually need to.

Before this change, the eventlistener pod(s), in OpenShift, would happily run with a random uid. With this change, the serviceAccount that runs the eventlistener pod(s) need to have the anyuid scc attached (see here)

The problem with #862 is that the behavior is not configurable, aka we can't disable it if we don't need it.
I propose to add a way to configure this behavior, most likely through a feature-flag (that would be enabled by default)

[MarcelMue]

I will try to provide a PR with a fix as I introduced the change.

[MarcelMue]

PR which adds a flag is open now. My main concern is that I am unable to test this properly - so would rely on someone trying this on openshift.

[MarcelMue]

I added some more unit tests and am fairly confident now, that this can be closed.

[vdemeester]

/close

[tekton-robot]

@vdemeester: Closing this issue.

In response to this:

/close

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