Allow to define VS Code extensions preferences in Che plugin registry

= The plug-in registry can define VS Code extensions preferences When a VS Code extension have not used environment variables, the user had to set the configuration in the devfile scope. For an extension to modify the configuration of another extension, the user had to create a separate plug-in embedding both extensions. With this release, the user can set default static configurations in the plug-in's `meta.yaml`. * An extension can modify the configuration of another extension. .Lombok and Java ==== The Lombok extension is defining configuration for the Java engine. ====