Flattening geometries to 2D before converting them to Esri geometry via WKB

Quick workaround for issues with Z-enabled coordinates. Probably not a definitive solution.

Also tried IGeometryFactory.CreateGeometryFromWkbVariant, which does not work either (gives exception: "wkb type is not one of point, multipoint, linestring, multilinestring, polygon, multipolygon, multipatch or geometrycollection").

If it is confirmed that IWkb.ImportFromWkb cannot handle Z coordinates, we'll have to find an alternative way of converting geometries to Esri, perhaps by reimplementing the WKB conversion altogether.