Feedback: Build out multi-region Kubernetes deployment documentation

Today, the multi-region deployment section for the CockroachDB Operator deployment is very bare bones. We should provide more details on how to test the network is configured correctly, options for configuration, principles behind what is needed, etc. We do not need to "boil the ocean" but help users build the internal understanding of the "methodology" behind what's required and then apply it to their specific infrastructure setup. For each cloud provider, we should provide explicit examples -- either in docs or in linked github repos.

Jira issue: DOC-15410