Add Advancement Renderers

[8s2]

This PR adds an API for registering custom renderers for advancement icons, frames, and backgrounds. Modders can use this to have extra fancy visuals for their advancement tabs.

There's some wacky mixins in here haha. I tried my best to make this as compatible as possible with any mod that may reformat the advancements screen.

[modmuss50]

Looks like a good start, I havent done an indepth review or looked at the mixins or testmod.

[sylv256]

aside from modmuss's requests, I made a few nitpicks.

[modmuss50]

Looks good, ill approve this and merge to last call. Just a few minor nit picks to fix before merging.

[MattiDragon]

Is there a reason why renderers get to pick which advancements they apply to instead of the opposite? Right now if someone else wants to use your renderer, they need to re-register it for their own advancement ids, and afterwards that cannot be undone.

Wouldn't it make more sense to add fields to advancements letting them pick renderers from a registry? This way datapacks and modpacks can easily pick from any renderers added by mods.

[8s2]

Is there a reason why renderers get to pick which advancements they apply to instead of the opposite? Right now if someone else wants to use your renderer, they need to re-register it for their own advancement ids, and afterwards that cannot be undone.

Wouldn't it make more sense to add fields to advancements letting them pick renderers from a registry? This way datapacks and modpacks can easily pick from any renderers added by mods.

I think this would put this PR out of scope for the rendering API module, so much so that it would probably require a new advancement API module, since it would require server-side changes too.

[sylv256]