Switch Festival of the Lost Mask to Mod Slot limitations

[TheYeshir13]

As has been discussed in #135, the Event Mask could also work with the same logic as the new guardian games class items

          The option would fit in with the one for Festival of the Lost, fwiw. Or FOL could switch to this pattern.

Originally posted by @abea in https://github.com/Mijago/D2ArmorPicker/issues/135#issuecomment-1534849408

• [ ] add a new slot for helmets only and let it return all eligible masks for the event
• [ ] Delete advance option to use FotL Mask