Create a new IR Node to represent TypeLiterals and NamedTypes

[adithyaselv]

Today we serialize the TypeLiterals and NamedTypes to strings and then deserialize it into DType in the runtime implementation of a function. Having a separate IR node for this would result in cleaner implementation and would avoid unnecessary Serialization and DeSerialization

[MikeStall]

+1. There's a related issue of how we pass the type into the function at runtime. Ideally, this would also be a dtype (and not a string to deserialize).