[Feature] Introduce a console literal for raw bytes

[ljedrz]

This PR is a draft/RFC proposal for a new console literal containing raw bytes, which would allow us to e.g. handle hashes (example use case) and proofs in Aleo programs.

Open points:

• does this proposal require an ARC?
• the encoding to be used in programs
  • it is currently a hex encoding for simplicity, but that incurs a 100% penalty in size when encoded
  • e.g. base64 would reduce that penalty to ~33%
• the length limit(s)
  • is u16::MAX enough/too much?
  • should the length prefix be an order of magnitude greater for potential future compatibility? this is the reason for the additional implementation in snarkvm-utilities
• a call to unimplemented!() in circuit::Literal::new
  • it is safe to make it unimplemented! as long as Inject::new is not intended to be used externally
  • this new feature could be extended with a circuit counterpart, removing the need for it