Move SerializeForVersion into the super module so it can be implemented on common types

[sistemd]

Currently, SerializeForVersion is defined in the dto::serialization module. For this reason, we need various odd wrappers to serialize common types, such as this TxnHash type, as well as many others added in #2178.

Instead, we can move SerializeForVersion into the dto module, allowing us to implement it directly on the common types and avoid the wrappers.

[sistemd]

Admittedly, another reason for these wrappers is to enable this blanket impl, but it's probably more elegant to make a Serde wrapper that delegates to serde::Deserialize and get rid of the blanket impl.