docs(deploy): operator handling of resources in namespaces

[PaulRMellor]

Documentation

Updates the operator and Kafka component deployment instructions to advice on the use of single namespaces for each deployment of the same component (such as when deploying multiple Kafka clusters)

• New section: Planning your Cluster Operator deployment: avoiding conflicts, watch options, isolating watched components
• New section: Operator-watched resources (table)
• Adds warnings about operand/component namespaces to Cluster Operator and Kafka component deployment sections
• Adds warning to TO and UO deployment sections
• Updates Operator overview to describe reconciliations
• Streamlines Cluster Operator deployment concepts

Checklist

Please go through this checklist and make sure all applicable tasks have been done

• Write tests
• Make sure all tests pass
• Update documentation
• Check RBAC rights for Kubernetes / OpenShift roles
• Try your changes from Pod inside your Kubernetes and OpenShift cluster, not just locally
• Reference relevant issue(s) and close them after merging
• Update CHANGELOG.md
• Supply screenshots for visual changes, such as Grafana dashboards

[scholzj]

Thanks for looking into this @PaulRMellor. I left few comments.

[katheris]

Thanks @PaulRMellor I agree with all of @scholzj's suggestions and don't have any further comments beyond those

[scholzj]

@PaulRMellor Did you forget to push the changes? (As you talk about them in the comments, but nothing was pushed)

[scholzj]

@PaulRMellor I have one nit/question about the formatting. LGTM otherwise.