feat(tvix/eval): implement equality operator

Change-Id: I9dd54aed72cd7e67593dc76f5a046ebbda40c26f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6078
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: grfn <grfn@gws.fyi>

tvix/eval/src/opcode.rs

@@ -17,13 +17,16 @@ pub enum OpCode {
     OpTrue,
     OpFalse,
 
+    // Unary operators
+    OpInvert,
+    OpNegate,
+
     // Arithmetic binary operators
     OpAdd,
     OpSub,
     OpMul,
     OpDiv,
 
-    // Unary operators
-    OpInvert,
-    OpNegate,
+    // Logical binary operators
+    OpEqual,
 }