New SeqN Category Introduction

[agureev]

Introduces a new category SeqN with appropriate API alongside with the compilation of it to appropriate Vamp-IR code. SeqN can be thought of as a category of finite sequences of natural numbers with morphisms from (x1,...,xn)to (y1,...,ym)being Vamp-IR functions taking in n entries of sizes x1 to xn and spitting out m outputs of sizes y1 to ym.

[mariari]

Yeah this needs work, I've fixed it up, but the mixing of the optimization with the code, makes it horrid to read. Please remove all optimizations and turn them into passes, this is too much