[1.12.2] Ability to toggle more generated structures

[muzikbike]

There's a few more structures from vanilla that can't be customized by either vanilla custom or CWG custom. It might be a good idea to add checkboxes for them to allow for more extensive customizability (at least when CC can handle their generation properly).

Structure list for Overworld structures:

• Grass, flower and mushroom patches (#45)
• Liquid springs (#40)
• Discs (#41)
• Trees, bushes and giant mushrooms (#53)
• Desert wells
• Fossils
• Cacti generation
• Sugar cane generation
• Desert pyramids (split from Temples)
• Jungle pyramids (split from Temples)
• Witch huts (split from Temples)
• Igloos (split from Temples)
• Buried treasure (1.13+)
• Ocean ruins (1.13+)
• Shipwrecks (1.13+)
• Kelp generation (1.13+)
• Pillager outposts (1.14+)
• Bamboo generation (1.14+)

[Barteks2x]

This would in general require ability to customize biome decorator values, which are per biome. This is going to be available eventually. Probably after 1.15.x version.