config structs require Serialize

[rukai]

This PR exposes all our config structs in the public interface and requires that they implement Serialize.
Additionally a serialize method is added to Topology which serializes the config into yaml.
The goal is to allow the programmatic generation of topology.yaml files.

Users could always just use some kind of yaml templating but if the code doing the generation is rust then this change will allow for a stronger typed solution.

This change comes at the cost of:

• a small increase to compile times, although I couldnt measure any change on my machine.
• larger public API surface to maintain
• custom transform config implementations now need to implement serialize as well deserialize.

We should consider this PR from a users perspective but it will also enable #1332