To detect which edges are dissolved in the extrude operation (with
"use_dissolve_ortho_edges"), it is necessary to inform a direction that
identifies which of the new faces are perpendicular to it.

Currently, this direction is the average of the normals of the selected
faces.

But this value must match the direction in which the selected faces are
moved, which can be unpredictable when the "Individual Origins" option is
enabled.

So this patch proposes to pass the direction as an argument from the bmesh
extrude operator. If this value is 0.0, 0.0, 0.0, the direction chosen
will be that of the adjacent faces.

Thus, when "Individual Origins" is enabled, the direction will be that of
the adjacent faces.

The ideal would be to calculate the average normal for each selection
island, but this would complicate the code a lot and is not really that
essential. Especially because the extrude manifold operator can be
replaced.

Ref T78635