Part of ##40867

Motivation:

* The work package attributes for % Complete for a work package has two values:
* The value for the the parent work package itself.
* The Begin of the insertiontotalEnd of the insertion Begin of the deletion aggregatedEnd of the deletion value, derived from the work package and its children attributes (before it was children attributes only)
* The Begin of the insertiontotalEnd of the insertion Begin of the deletion derivedEnd of the deletion value computation depends on the work, the status, and the % Complete attributes of the work packages
* a work package with work being 0h or unset is excluded from computation

See subtasks below