Fix breaking changes introduced by Slimefun for 1.21

[alexsvorada]

CustomItemStack from dough is no longer an ItemStack, but a helper class to create ItemStack.
suggested change: Change new CustomItemStack(...) to CustomItemStack.create(...). Most constructor parameters are kept in the same order.
SlimefunItemStack is no longer an ItemStack but a delegate of ItemStack.
to get the underlying ItemStack, use .item()
The ItemStack instanceof SlimefunItemStack no longer makes sense, use SlimefunItem.getByItem() to get the SlimefunItem instance.```

Fixed the issues caused by these changes

[alexsvorada]

How should the backward compatibility be done?
Create static vars in ExoticGarden and wire the proper value based on the MinecraftVersion in onEnable?

[alexsvorada]

Also can you help me understand why are we maintaning backward support for an enum that has been changed 4 major updates ago?