[docs] address recommended ways to manage production deployments

It's not entirely clear from the docs how skaffold should fit in with IAC tools.

If I'm understanding correctly, unlike an IAC tool, skaffold won't track cluster state and e.g. delete a service that has been removed since the last deploy. helm (a supported deployer) provides such functionality, but is too heavy-weight for many applications. It seems that (e.g.) pulumi users could use skaffold just for rendering yaml, then manage deployments (pardon the overloaded term) with pulumi.

If this kind of lifecycle management is considered out of skaffold's scope, that's understandable, but it seems worthwhile addressing IAC integration options in the documentation since most skaffold users will face this question, and "deployment" as a broader concept/action is within skaffold's scope.