Add FullType pooling/caching system #37
Description
Right now the code creates A LOT of FullType, which is essentially a type with the modifiers, such as pointers and array modifications.
We still need to be able to pump these types, but it would be convenient to cache types, such that we can cache the type generation in the SPIRV backend as well.
My initial suggestion is finding a hashing method for the type itself, and store all previously created types in a hash table. This hash can then be used in the SPIRV generator to get hashed types without having to unroll and recursively create every subtype.