Werk #11045: Optional package: Replace Kubernetes extension package

This change replaces the optional extension package k8s_ingress_and_job_info for Kubernetes by the extension package k8s_extensions.

It fixes the bug that the Kubernetes Ingresses and Jobs could not be selected in the datasource ruleset of the former extension package.

Furthermore, the ruleset now contains an option to use a namespace prefix for the hosts that are created in Checkmk and Endpoints can now be monitored.

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