1.21.6 port

[eristhea]

all work done by @A5ho9999 and @orifu ! thank you so much :)

original description:

Not much changed in terms of logic, just remapped unmapped stuff and trimmed the fat for the variant provider (since no longer exists in vanilla)

• Updated Dependencies + Loom/Gradle
• Updated the mappings so it's no longer unmapped methods/classes
• Removed the separate Variant Providers and added a single one with get and set
  • Since variants are data driven now, the VariantProvider from vanilla is gone

Not done any bug testing outside for loading a world, spawning & saving/loading