Review codebase for gas optimizations related to inefficient Enum storage

[loothero]

Currently Starknet uses an entire felt to store the variant of an enum. This is true even if you have an enum with only a couple variants such as

enum Color {
     blue,
     yellow,
     red
}

As such, it's highly inefficient to store enums directly. I see two good options:

1. If Cairo/Starknet allows it, implement StorePacking on the Enumerator to provide more specific instructions on packing.
2. Otherwise, use u8 for storage and convert to Enum after taking out of storage.

Note, for models which is infrequently written to, this is a non-issue. Focus instead on models which are written to most frequently, with the goal of getting those to one or two felts.