[FEAT] Improvements required to support "style the BPMN traces/paths"

[csouchet]

This issue relates to #930

Improvements on the internal model

Beta Give feedback

1. [FEAT] Include links between edges and shapes in the internal model #2503
   BPMN support enhancement +2
   
2. [REFACTOR] Keep the loaded BpmnModel into memory #953
   refactoring +1
3. Add parent/children hierarchy? currently an element only knows its parentId
4. Expose the model (internal or a dedicated one) via an API. This lets users and third party libraries manipulate the model and manage the paths.
5. [FEAT] Add new methods to only retrieve the BPMN semantic of elements in the model #2813
   2 of 2
   BPMN diagram usability decision record enhancement +3
   

See process-analytics/bpmn-visualization-examples#433