Proposal: Union all the interfaces

[malcolmstill]

Description

If Tagged Unions don't take up the space of the largest type (I'm not sure if they do or don't yet). Then we could unify all the interfaces, such that we would get more type safety in certain circumstances.

We could also then generate the Object inputs to dispatch functions to be of a particular type.

This would involve generating the protocol such that we have distinct structs for the different interfaces