chore: remove Immediate from Immediate::{Word, Byte, Operand}

It's already clear that its an Immediate value
without the prefix.

src/register.rs

@@ -1,6 +1,6 @@
 use core::fmt;
 
-use crate::instructions::ImmediateOperand;
+use crate::instructions::Operand;
 
 #[derive(Debug, Clone)]
 #[allow(dead_code)]
@@ -35,9 +35,9 @@ pub type RegisterId = u8;
 #[allow(dead_code)]
 impl Register {
     /// Find the register corresponding to the 8086 bytecode ID
-    pub fn by_id(id: ImmediateOperand) -> Self {
+    pub fn by_id(id: Operand) -> Self {
         match id {
-            ImmediateOperand::Byte(b) => match b {
+            Operand::Byte(b) => match b {
                 0b000 => Self::AL,
                 0b001 => Self::CL,
                 0b010 => Self::DL,
@@ -48,7 +48,7 @@ impl Register {
                 0b111 => Self::BH,
                 _ => panic!("Invalid 8bit register ID encountered"),
             },
-            ImmediateOperand::Word(w) => match w {
+            Operand::Word(w) => match w {
                 0b000 => Self::AX,
                 0b001 => Self::CX,
                 0b010 => Self::DX,