Add `Subscription delta` for modify workflows

[wouterhhuisman]

After a modify workflow has been run or if halfway the WF failed, it can be quite useful to see what the actual modification was. By performing a deep-diff on the subscription with the old_subscriptions and presenting it in a gitlab view (- and + highlighting) it will become instantly clear what the change comprised.

• The delta view is available on the process detail page for processes with the workflowTarget=MODIFY.
• Not available for processes with isTask=true

• only show subscription delta button, when workflowTarget=MODIFY
  
• perform a deep diff on the subscription for which the WF is being run. Use the subscription_id from the __old_subscriptions__ and compare with the subscription found in the last step state.
  • ensure that difference in sorting order is reflected as a delta
• to maximize the view width, open a modal and show the old and new subscription side by side, like presented in the design:

• add header with the subscription_id and subscription description
• hide unchanged rows after 3 exact rows - like gitlab show the commit changes
• Don't include the copy or maximize buttons, that is nice to have R2+ features
• don't show the delta, as the side by side comparison is good enough, and is 100% clear on additions and deletions.

When choosing a new library, discuss with other developers

Use a library to present the delta in way that the additionas and deletions become instantly clear. Consider for example https://github.com/praneshr/react-diff-viewer#readme or https://github.com/otakustay/react-diff-view

[acidjunk]

Started with the first suggestion, but it;'s unmaintained:
praneshr/react-diff-viewer#166
So switched to the fork which seems to be maintained.

React Diff Viewer uses emotion for styling. So very the