refactor: remove string types

[zmalatrax]

Solves #51, using enums

• Rename OpLogic to ResLogic, name used in the cairo whitepaper
• Rename RegisterFlag to Register (seems ok but RegisterFlag might actually be more clear and should be kept)
• Cleanup of unused import/errors previously missed out
• Rename 'unconstrained' to ResLogic.Unused as in the cairo whitepaper, which is easier to understand
  However, this entry might be removed in a future refactor on the operand computation (currently 'compute/deduce' vs more straightforward as in the cairo vm gs)
• Export instruction instantiation in const objects in virtualMachine.test.ts to reduce duplicate code and provide cleaner test cases
• Constant called from the class rather than the instance (this.BIAS --> Instruction.BIAS)
• Add JSDoc to enums with their Cairo Assembly equivalent (as in the Cairo whitepaper State transition, except for Jnz which uses a js ternary operator to show the if-else control flow)

The classes Instruction and VirtualMachine still need to be refactored but it is for another PR, as well as adding proper JSDoc to the different classes.

[ClementWalter]

I left some comments but this can be tackled later on. We need to simplify this whole instruction thing, over complicated here