[1.18.2] Bosses and other entities rework, general rebalancing

[Minecraftschurli]

Leaving this here to make review easier later: Review only .java Files

[Minecraftschurli]

I sent you a patch to address my comments

[IchHabeHunger54]

Gonna do a separate bump PR that also contains the changelog once #335 is merged.

[Minecraftschurli]

bump needs to happen first not last for a new version or else the maven version for these changes are under the old version (which would be a breaking change inside the same version)

[IchHabeHunger54]

ok fair enough