[kbn/optimizer] print warnings about circular dependencies between plugins

[spalger]

In #68986 we almost removed the ability to have circular dependencies between plugins, but found the code changes necessary to get there to be too daunting. We are instead going to tackle them in chunks, after that PR is merged, but it would be useful if the @kbn/optimizer could warn users about the circular dependencies it detects. It might be pretty noisy, so we may want to make it opt-in, or limit the log messages to the bundles that were actually changed on build events after a watch. We might have trouble identifying circular deps between portions of a bundle, as all of the exports from a bundle might be totally independent, but have circular deps within that might cause issues... So some experimentation will be required.

[elasticmachine]

Pinging @elastic/kibana-operations (Team:Operations)

[tylersmalley]

Believe this ask was completed by preventing circular dependencies here #82867