This fixes the existing DI creation methods in `BpmnFactory` and
simplifies the related `ElementFactory` code that relied on it.
In the past args got ignored and passing attrs to the created DI
was not possible, now it is.
BREAKING CHANGE:
With this change the following `BpmnFactory` API methods got reworked to
take (businessObject, attrs) as an input:
* `BpmnFactory#createDiEdge`
* `BpmnFactory#createDiShape`
* `BpmnFactory#createDiPlane`