Bind process to localhost only if demo certificates are used

[setiah]

Related to opensearch-project/OpenSearch#1618

The ask here is to bind the OpenSearch process to only localhost if demo certificates are being used. This would put essential guardrails on using the insecure demo certs by dis-allowing public traffic and restricting the use only for dev/testing purpose.

Please note - This is an optional FR for now, as the demo certificates may end up getting deprecated altogether.

[setiah]

This could be an issue for existing users using demo certs, when migrating to latest version with rolling upgrade as the binding might prevent cluster formation. An easier path forward would be deprecating the demo certificates itself. Closing this out for lack of better data points in favor of this.