[FEAT] Enrich links between edges and shapes in the internal model

[tbouffard]

Is your feature request related to a problem? Please describe.
In #2503, we added the incoming/outgoing information taken from the BPMN Semantic. But as suggested in #2520 (review), these attributes are not mandatory and not always set by BPMN Modelers on the flownode objects.
So, the information may not be always available so not present in the internal BPMN model.

Describe the solution you'd like
For all flows, the source and target references MUST be set. So we could use them to enrich the internal model:

• take the incoming and outgoing information as introduced with [FEAT] Include Flownodes incoming/outgoing in the internal model #2520
• after flows have been parsed, enrich the incoming and outgoing arrays in the internal model by deducing flow/flownode links from the sourceRef/targetRef values of the flows

Notice that this solution will make the information available for pool/participant and text annotation. The BPMN semantic doesn't describe the incoming/outgoing links for such elements

Describe alternatives you've considered
If we don't do the extra mile, the incoming/outgoing properties will be empty for a set of diagrams. We plan to base the "2023 paths related features" on this information, so this will defeat a major improvement we want to implement this year.

Additional context

Most of the work will consist of creating new automated tests.

Tasks

Beta Give feedback

1. Ensure we don't duplicate information coming from incoming/outgoing (directly taken from the BPMN Semantic) and the computed values (from the flow sourceRef/targetRef).
2. Enrich tests for all existing flownodes : they must check that when the parsing using info from flows when no incoming/outgoing is defined
3. Add tests for pool and text annotation