This patch adds a 'Intersecting Edges' output with a boolean selection
that only gives you the new edges on intersections.
Will work on a couple of examples next, this should make some
interesting effects possible (including getting us closer to the "bevel-
after-boolean-usecase")
To achieve this, a Vector is passed to `direct_mesh_boolean` when the
iMesh is still available (and intersecting edges appended), then from
those edge indices a selection will be stored as attribute.
Differential Revision: https://developer.blender.org/D15151
e2975cb701