Redesign Request Parsing and Intermediate Representation Signatures

[dchoi-viant]

Currently, the primary evaluation endpoint provides a contract that supports multiple forms of "polymorphism."

1. It does not have a completely defined set of key values, i.e. is dynamic.
2. It enables object values to be either arrays or scalars.

While the key value definition dynamicism is fine, the array-scalar conjunction should be pushed to a separate endpoint.

[dchoi-viant]

Additionally, we should be considering how we generally convey data and use []interface{}/any in fields. Specifically, the current []interface{} in service.Request.Feeds is a general development pain-point, both in understanding the code and the amount of boilerplate it introduces.