[kbn/optimizer] Only allow refs to bundles described in kibana.json

[spalger]

With #68986 merged the optimizer is much faster because cross-plugin imports are now transformed into references to the bundles from other plugins at buildtime. This is functional, but causes implicit dependencies to be created between the bundles. This causes problems when users start disabling plugins as a disabled plugins bundle is not loaded into the browser, but if another plugin imported code from that plugin it needs to be loaded into the browser or else we get a runtime error about a missing bundle.

To fix this we will make the relationships between bundles more explicit by defining a set of requiredBundles in the kibana.json file. Any plugin id listed in the requiredBundles list will have its bundle loaded into the browser, but the plugin itself will still only be loaded when the plugin is enabled via config.

Example issue that would be solved by this: #69394

[elasticmachine]

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