Problem

If you copy & paste a collapsed subprocess with some elements inside and try to undo this action, editor crashes.

Root cause

When a collapsed subprocess is pasted, elements.create command is triggered and triggers following actions:

1. shape.create for a new subprocess element.
2. elements.move for subprocess children (triggered post-shape.create by `SubProcessPlaneBehavior)
3. shape.create for each child.

When this action is being undone, subprocess children are first removed (revert shape.create) and then are attempted to be moved back to their original parent/position (revert elements.move) which doesn't make sense as those elements are already removed.

Proposed solution

I believe the correct implementation of subprocess plane behavior should move the elements onto the new plane after they are all created, so on postExecuted of elements.create instead of shape.create.

This pull requests does it and therefore solve the paste & undo bug.

New problem

Unfortunately, the subprocess element in the context of elements.create handler doesn't have all its children. It's missing labels and text annotations. Those elements are still copied, but remain hidden on the root plane.

Additional context

Initial discussion and debugging session: bpmn-io/diagram-js#957 (comment).

Closes #2269

Checklist

To ensure you provided everything we need to look at your PR:

• Brief textual description of the changes present
• Visual demo attached
• Steps to try out present, i.e. using the @bpmn-io/sr tool
• Related issue linked via Closes {LINK_TO_ISSUE} or Related to {LINK_TO_ISSUE}