PIM UI - process nodes mapping screen issues

Currently, when defining a migration plan the way of mapping nodes between two process definitions is unwieldy.

The current state does not follow UX design as presented in JBPM-8015.

This tracker lists issues with the particular screen, each of the items can be turned into child issue.

1. First, user needs to select node from a drop-down by its title and id. The selection of nodes should be ideally performed by clicking nodes in the diagram, which is not possible.
2. When selected from the drop-down, the element shows only the id, which is a generated user non-friendly value.
3. The pairs of already mapped nodes are presented to the user as a plain JSON object, which is not acceptable, user has no overview of already defined node pairs.
4. For the purpose of node mapping, seeing the diagrams side-by-side would improve usability
5. One source node can be mapped to more target nodes. This results in multiple mappings in resulting JSON. That should be actively prevented in UI (i.e. removing the already mapped source node from the drop-down, or overriding the existing mapping)
6. Process diagram widget has serious usability issues:
   • process diagram is small, should probably best fit the area
   • diagram controls are not intuitive (while shifting, zooming, ...)
   • when moving the diagram within the widget, whole canvas is moved leaving the background grey
   • when zooming, user needs to click zoom icon then click the diagram for each zoom step (click icon -> click diagram -> click icon -> click diagram -> click icon -> ....)