Use custom serialization and deserialization to recompute the cached hash code

[gafter]

We should use custom serialization and deserialization to recompute the cached hash code unless we can guarantee that they are stable.

[gafter]

For customizing Julia's base serialization, I think one needs to specialize

• Serialization.serialize(s::AbstractSerializer, md::TypeToDeserialize)
• Serialization.deserialize(s::AbstractSerializer, T::Type{TypeToDeserialize})

See also

• raicode/packages/MuttsDicts/src/serialization.jl
• https://docs.juliahub.com/JLD2/O1EyT/0.4.31/customserialization/