Don't unnecessarily copy extruder stacks to list
Don't unnecessarily copy extruder stacks to list

You're just looping over it. No need to actually make a list out of it.

Contributes to issue CURA-3291.

hmflash/Cura,Curahelper/Cura,hmflash/Cura,ynotstartups/Wanhao,fieldOfView/Cura,ynotstartups/Wanhao,Curahelper/Cura,fieldOfView/Cura