fix(subprocess): Improve subprocess behavior

A collapsed subprocess has non-visible child elements
and an expanded subprocess has visible child elements.

An expanded subprocess has always the correct size to
show all child elements.

Add test cases to check this  improvement.

Delete Pullup and Pushdown feature from context menu.

related to #CAM-1500
Merge branch 'master' of github.com:camunda/camunda-modeler
Merge branch 'master' of github.com:camunda/camunda-modeler