feat(tazjin/rlox): Implement unary negation operator

Change-Id: I9a5bd3581d4ed05371651697ec496341eb7971ae
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2572
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

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

@@ -11,6 +11,9 @@ pub enum OpCode {
     /// Return from the current function.
     OpReturn,
 
+    // Boolean operators
+    OpNot,
+
     /// Unary negation
     OpNegate,