Issue #2784921 by amateescu, timmillwood, pk188, plach, catch, Fabianx, dixon_, dawehner, borisson_, Sam152, yoroy, webchick, phenaproxima, larowlan: Add Workspaces experimental module

Issue #2941622 by Wim Leers: Make REST's EntityResource deriver exclude internal entity types and mark ContentModerationState entity type as internal instead of the current hack

Issue #2843753 by Wim Leers, amateescu: Prevent ContentModerationState from being exposed by REST's EntityResource