Detach `MutationSettings` from specific `NeuralNetwork` instances.

[HyperCodec]

In most cases it ends up just being extra cloned data. There's never really a reason for some networks to have different mutation settings than others, could prob use statics or something (statics bad). Might require adding more features to genetic-rs to allow simulations to contain arbitrary settings that crossover/division reproduction functions can access.

[HyperCodec]

The changes in this new sub-issue could also potentially be used to eliminate the statics from the activation registry. Don't know what to do about serialization/deserialization though.