[Interchange][FBX] Import of custom collision add the collision mesh material slot to the mesh material slot

cf part 2 of that UDN

https://udn.unrealengine.com/s/question/0D5QP00000rP4CG0A0/interchange-custom-collision-changes-from-fbx-pipeline?fromCase=1

Import the attached FBX file with interchange FBX enabled

Open the static mesh and check its material slots.

1) The "MaterialUCX" slot is there when it should not have been imported

2) No material asset related to the collision mesh should be created either