feat(hatchery): allow eggs and fossils in queue

[shallotmama]

Adds the ability to put eggs and fossils in the queue.

Closes #1362

[shallotmama]

[Jaaslet]

(Have not tested it yet. Just took a quick look) The breeding window still has both the "full queue" and "no empty slots" warning. I don't think there are any situations anymore, that only cares about empty slots? So we should remove that. And the implementation looks cool! It's how i would had made it, if i ever found time to do it.

[shallotmama]

The three types are all string literal union types pulled from enums, so they don't make sense as their own classes. I did a little cleanup though, and I think it's a lot clearer now.

The main complication was that EggItemType and the image files use the format of <type>_egg while everything else just uses the type name. I don't know why I was doing the weird conversions instead of just doing it the way it is now. 😆

[Aegyo]

This PR has gotten a bit stale and collected a bunch of conflicts (our fault, sorry about that), I'm going to close this one and if you are still interested in doing this you can redo/rebase your current work over the latest develop and open a new PR.