feat(tazjin/rlox): Support trivial literals in bytecode compiler

Adds support for true, false & nil. These each come with a new
separate opcode and are pushed directly on the stack.

Change-Id: I405b5b09496dcf99d514d3411c083e0834377167
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2571
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

users/tazjin/rlox/src/bytecode/vm.rs

@@ -72,6 +72,10 @@ impl VM {
                     self.push(c);
                 }
 
+                OpCode::OpNil => self.push(Value::Nil),
+                OpCode::OpTrue => self.push(Value::Bool(true)),
+                OpCode::OpFalse => self.push(Value::Bool(false)),
+
                 OpCode::OpNegate => {
                     let v = self.pop();
                     with_type!(