Slab Refactor, Leaf Refactor, and Everything Burns

[Ruling-0]

In which I go from an issue which says "just uncomment this line" to finishing part of the 1.7.10 migration of Natura, 10 years later.

First, slab refactor. Natura slabs now inherit from the base BlockSlab, and can now do things like double stack!

Those aren't blocks, they're double slabs

I've also updated the log block updates to correctly mirror 1.7.10 logic (it was outdated) and removed the leaf logic (it was also outdated and at best not doing anything, at worst keeping leaves from not decaying when manually placed). Leafs now also have proper metadata functions, which means pick block works correctly and certain leaves no longer autodecay when manually placed.

Finally, now everything burns. Those double slabs previously?

The nether woods are fire immune.

This applies to all the wooden products, even fences!

And now, you can finally give that redwood tree the treatment it deserves.
https://github.com/user-attachments/assets/28493878-73a9-4bf8-b4d0-bfa6ce637bad

fixes GTNewHorizons/GT-New-Horizons-Modpack#9644
fixes GTNewHorizons/GT-New-Horizons-Modpack#18640

The deleted files are unreferenced classes.

[Ruling-0]

Fixed the extra Eucalyptus double slab bug. Copying how the vanilla BlockWoodSlab handled subblock registration apparently doesn't work in the modded case. I assume the vanilla version is part of how double slabs are hidden in NEI, but these and BoP's remain. Or that's a separate NEI thing.

[Ruling-0]

Updated to fix GTNewHorizons/GT-New-Horizons-Modpack#18640 by fixing issues with leaf metadata handling being incorrect.