[1.21.3] Add conventional tag for animals

[PaintNinja]

Preliminary Forge port of FabricMC/fabric#4168 and neoforged/NeoForge#1596.

As per Forge's policy, I'll merge this once the other loaders merge it. This only applies to 1.21.3 at the moment, as there aren't backports of this tag to older versions of both of the other loaders yet.

[Jonathing]

It might be prudent to potentially consider backporting new tags to 1.21.1 while it is in full support. Strictly additions, not any changes to existing tags. Cross-version datapacks are pretty much a standard nowadays.

[PaintNinja]

While I understand the appeal, I promised in the common tags announcement that Forge will guarantee to only have c tags that are common across all loaders for a given version, to avoid the surprising scenario of a tag not working on some loaders but only on specific MC versions.

However, seeing how Forge’s support lifecycle exceeds that of the other loaders, I don’t expect any trouble in backporting new tags to older Forge MC versions if/when the other loaders do as well.

[Jonathing]

While I understand the appeal, I promised in the common tags announcement that Forge will guarantee to only have c tags that are common across all loaders for a given version, to avoid the surprising scenario of a tag not working on some loaders but only on specific MC versions.

Ah, I forgot that part of it, my bad.