Fix #1178 - Remove Kogito Operator pipelines and references

[ricardozanini]

See apache/incubator-kie-kogito-operator#1537

I've kept the node and the image that builds the operator 'cause we reuse it for the SonataFlow operator too.

Also, the example-images pipeline CAN be disabled since we only use it for the Kogito Operator BDD. But we need a new assessment on it to understand if they are being used somewhere else. We can open another PR to take care of it.

[jstastny-cz]

@ricardozanini IMHO the example images were exclusively for operator BDD tests. Let's ask @radtriste to confirm and we could get rid of it already.

[radtriste]

As far as I remember, they were mostly used for the bdd tests. We were indeed pushing them but I don't think that we were mentioning them into the documentation and/or examples' readmes.
That should be easy to check (look for 'quay.io/kiegroup/example-*' string

[rodrigonull]

LGTM.

[ricardozanini]

@radtriste @jstastny-cz many thanks for the updates! I'll remove the Jenkins Node and the BDD tests. I'll also squash this commit to make it easier to grab anything back if needed.

[ricardozanini]

@jstastny-cz @radtriste can you please take a look to make sure that my exclusions are alright? Thank you!