[467] Fix edge creation tool regressions

[mPorhel]

Bug: #467

Fix regressions introduced with #470 :

• Regression identified in
  • HideRevealEdgeLabelsTest
  • EdgeCreationPositionTest
  • EdgeCreationPositionWithSnapToGridTest
  • EdgeWithBorderNodeCreationPositionWithSnapToGridTest
• The provided fix does not handle the extra mapping cases (edge tool creation two border nodes + an edge for example)
  • completing the introduced validation on source/target would be touchy : extra mappings, mappings imports, complex structure created by tools.
• The validation of the createDEdgeTask which automatically creates an edge from the EdgeCreationTool should check the semanticElement of the edgeCandidates rather than the correspondance of the clicked sourceView/targetView and the candidate sourceView/targetView.

The idea of the new fix is not follow the previous logic of CreateDEdgeTask

• it is slightly different from CreateDNodeTask/CreateContainerTask which directly creates the DNodeCandidate from the detected created elements.
• the CreateDEdgeTask analyses the semantic elements which are created or affected by its model operations in order to find possible EdgeMapping for those semantic elements using the BestMappingGetter
  • the use of sourceView/targetView in this object is partially unclear: it depends on the number of mappings referenced by the tools, the mapping precondition is not checked if there is only one mapping, ...
• Then it asks a DDiagramSynchronizer to compute EdgeCandidates
• in AutoRefresh / tools::forceRefresh : the refresh task will potentially add new elements or delete invalid created DEdges.

In #470, the check added on clicked sourceView/targetView is too restrictive. Regarding how the edge mapping to "refresh" are found, checking that candidates for those mapping have the expected semantic candidates seems to be a better approach.

I have proposed avoid multiple coputation of DEdgeCandidates if several semantics have the same mapping, and to ensure reproductibility by replacing some HashSet with LinkedHashSet.

[mPorhel]

Pb in the message on the first commit, it seems you want to list the tests: However several use cases have been broken with unit tests: ???

Message update with the tests: HideRevealEdgeLabelsTest EdgeCreationPositionTest EdgeCreationPositionWithSnapToGridTest EdgeWithBorderNodeCreationPositionWithSnapToGridTest