Detect whether the current infill is gradual
Detect whether the current infill is gradual

And highlight the correct infill button in that case.

Contributes to issue CURA-3732.

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