Currently for each chain we have to create all of the Asc (AssemblyScript) types in the graph-node runtime.

This not only requires defining the types and fields themselves, but also to implement a few traits/interfaces, such as ToAscObj and FromAscObj.

Those should be automated via macros so that we have:

• Less code overall (remove all conversion code related to ToAscObj/FromAscObj)
• Less code required for adding new types + fields on the runtime (reduce developer time necessary on those)