Make spawn egg colours visible

[luisc99]

Adds an unsafe method for getting the underlying colour definitions for spawn eggs, based on the entity type. I recognise this is probably a fairly niche thing, but it can be useful to have a consistent way of getting some colours for entities when doing certain visual effects.

I've added this to UnsafeValues as it's accessing data directly from the SpawnEggItem class rather than reading data from an individual ItemStack's meta, although I'm happy for it to be moved somewhere more appropriate if desired.

The code is based on ItemFactory#getSpawnEgg, as found in this patch.

[yannicklamprecht]

Please squash commits in each submodule and rebuildPatches.

[luisc99]

Whoops, didn't notice it made a new patch, fixed

[Warriorrrr]

I think it might be nice to add getters for the background & highlight color to spawn egg meta, but currently also lgtm

[Machine-Maker]

If this wasn't in Unsafe, I would have some comments, but I think since it is, and therefore API compat isn't guaranteed, I think its fine.

Perhaps some more stable API can be added once we have subtypes of ItemType and BlockType in the API.