Add error if spawn placements are missing for entities that spawn in-world

[ThatGravyBoat]

Description

This PR adds an error in dev if there are any entities added to the MobSpawnSettings for biomes and the entity does not register a spawn placement. The reason for this is that if you do not register a spawn placement the entity can spawn anywhere which includes in the are and is usually a bug 99.9% of the time and can be hard to track down if a developer does not know where to look and does not know they need to register to such an event this logging will help with such an issue and help prevent such bug from reaching production. If a developer does need to not have their entities restricted they can register with NO_RESTRICTIONS as what vanilla does if none is registered is just default to NO_RESTRICTIONS and always true for the predicate.

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