Show diff of process variables after execution

[jarekdanielak]

Is your feature request related to a problem? Please describe.

It should be clear to the user how the process variables changed after the task executed.

Describe the solution you'd like

Based on the discussion in #12 and Slack, we could introduce a well-known diff view:

Describe alternatives you've considered

More ideas can be found in #12.

[philippfromme]

I'll move this to backlog. Not going to ship in 8.9.

[jarekdanielak]

I wonder, with the new task testing layout, is this still going to be relevant?

[philippfromme]

Might or might not. Let's keep it in the backlog for now.