Blender Git Loki

Outliner: Unified delete hierarchy operator

This resolves T73673 by allowing delete hierarchy in all outliner view
modes. It also unifies the collection and object hierarchy delete into a
single operator like in rBae98a033c856. This makes it easier to delete
all selected collection and object hierarchies at once.

This also removes the old object delete hierarchy code in favor of the
batch delete code which has been default for over a year.

Maniphest Tasks: T73673

Differential Revision: https://developer.blender.org/D7675