`BKE_modifier_get_evaluated_mesh_from_evaluated_object()` used by
modifiers needing access to other objects' geometry probably skipped out
of the radar when cage and final evaluated meshes were added to
BMEditMesh? In any case, we do not need to duplicate (and then free!) a
temp mesh from editdata anymore, and we can even add instead a parameter
to get cage instead of final. Also makes modifiers code a bit simpler.
7cca0f9998