pub fn from_byte(byte: u8) -> Opcode {
        unsafe { std::mem::transmute(byte) }
    }
Convert a raw byte to an opcode.
Note that non-opcode bytes should never be interpreted as an opcode.
Under the hood, this is just a transmute, so the regular cautions apply.
This *should* never cause a crash
and if it does, the vm's designed to crash hard
so it'll be pretty obvious.
passerine-common/src/opcode.rs