[LWFXEF] Change EObjectBasedDiagramControllerBase to work on EObjects

The type checks and model change providers have been edited in order for
the class to actually work with `EObjects`:
* The `EObjectBasedDiagramControllerBase` has been changed to require
`EObject`s only (not `IHierarchicElement`s).
* The `HierarchicModelElementModelChangeProvider`has been changed to
require `EObject`s only and has thus been renamed to
`EObjectModelChangeProvider`.

Issue-Ref: 3890
Issue-Url: https://af3-developer.fortiss.org/issues/3890



Signed-off-by: Tiziano Munaro <munaro@fortiss.org>