Publish dxDiagram types, arrange "commands" props types (T1227506)

[mpreyskurantov]

• all enums / unions: @public + @namespace DevExpress.ui.dxDiagram (with the dxDiagram scope - to avoid naming conflicts in a bundle similar to the other components, but we may keep DevExpress.ui only, because all these types start with Diagram)
• dxDiagramCustomCommand: @public (@namespace DevExpress.ui already exists - no the dxDiagram scope - the type name already starts with dxDiagram, i.e., an unique / component-basis prefix)

All published types become available in framework packages re-exports

• all props, which can be of both types Array<dxDiagramCustomCommand>|Array<Enums.DiagramCommand> - now have this type in d.ts (Array<dxDiagramCustomCommand | DiagramCommand>) without doc tag override (note that in react we cannot add a real enum / union type import, but use indi acc values instead, otherwise - BC)
• correct demos, where affected props refer to input values with as any