[Port] [1.21.10] Port to 1.21.10

[Minecraftschurli]

• Ports the mod to Minecraft 1.21.10
• Adds ageable copper variants of fancy lamps and fancy lanterns ([Suggestion] [1.21.9/1.21.10] Copper variants of fancy lamps and fancy lanterns #34)

[IchHabeHunger54]

Looks good content-wise, some minor nitpicks. Also some code style changes I'd like to see applied:

• No package-info.javas, they're insanely bloaty without really contributing anything imo.
• All classes in the datagen should be final.
• When putting annotations such as @Nullable on a field or method, put it above, don't inline it after the access modifier. I marked this in some places, do it in other places as well. Also applies to e.g. the @Unmodifiable annotation.
• Why are you using @UnknownNullability? If I understand JSpecify correctly, that annotation shouldn't really be used since it's the default value anyway.
• Run Optimize Imports on the entire thing after applying all other changes.
  Also, why exactly are we doing feature flags...?

As a sidenote, due to the complexity of the changes and me not yet looking into them, I haven't had a look at the following so far:

• All BERs
• The various model changes, including datagen
• Some parts of the Fancy Crafter and the Printing Table
  I will hopefully get to reviewing them soon.

[IchHabeHunger54]

Wouldn't just setting abnormalsCompat to false also work?

[IchHabeHunger54]

I'm honestly not a fan of this. If it's not easily possible to copy the block tags, can we maybe just copypaste the block tag gen here and replace Block with Item? This BlockToItemConverter feels overengineered for no reason.

[Minecraftschurli]

this is copied vanilla code

[IchHabeHunger54]

Move to a separate class, there really is no point of an inner class here.

[Minecraftschurli]

Except being nicer to read than a single long class name GroupedHolder.Nested > NestedGroupedHolder

[Minecraftschurli]

No package-info.javas, they're insanely bloaty without really contributing anything imo.

We need to specify a default nullability somehow and we can't use module-info.java yet.

When putting annotations such as @Nullable on a field or method, put it above, don't inline it after the access modifier. I marked this in some places, do it in other places as well. Also applies to e.g. the @Unmodifiable annotation.

Not possible when using JSpecify

Why are you using @UnknownNullability? If I understand JSpecify correctly, that annotation shouldn't really be used since it's the default value anyway.

only if you don't have a package-info.java or module-info.java stating a default nullability (either everything not null or everything nullable) which is to be preferred over unknown by default.

Also, why exactly are we doing feature flags...?

I was experimenting and hiding stuff that I didn't finish behind the flag