Evaluate "Unparsed" schema approach

[mattp-swirldslabs]

As a Block Node developer
I want to leverage an alternative schema to selectively "shallow parse" protobuf off the wire
So that we can reduce the cost of marshalling all of the objects while also improving maintainability by using an alternative schema rather than the low-level Bytes API.

While discussing the low-level approach using the Bytes API, Jasper thought we might be able to leverage a different schema to handle selectively parsing levels of objects from the top-down rather than parsing by hand.

Tech Notes

• Add a new unparsed.proto file to the stream subproject to specify new types
• Establish the relationship between the new types that mirrors the spec outlined in hedera-protobufs but relies in the bytes keyword in the definitions to stop PBJ and protoc from processing its children
• Gradle's behavior in the stream subproject may need to change to generate types based on the local schema