[interpreter] Introduce binary op bytecodes for Smi operand.

test/cctest/interpreter/bytecode_expectations/AssignmentsInBinaryExpression.golden

 #
 # Autogenerated by generate-bytecode-expectations.
 #
 
 ---
 pool type: string
 execute: yes
 wrap: yes
 
 ---
@@ skipping 181 matching lines @@
 handlers: [
 ]
 
 ---
 snippet: "
   var x = 10, y = 20;
   return x + (x = 1) + (x + 1) * (y = 2) + (y = 3) + (x = 4) + (y = 5) + y;
 "
 frame size: 5
 parameter count: 1
-bytecode array length: 65
+bytecode array length: 64
 bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   42 S> */ B(LdaSmi), U8(10),
                 B(Star), R(0),
   /*   50 S> */ B(LdaSmi), U8(20),
                 B(Star), R(1),
   /*   54 S> */ B(LdaSmi), U8(1),
                 B(Mov), R(0), R(2),
                 B(Star), R(0),
   /*   68 E> */ B(Add), R(2),
                 B(Star), R(3),
-                B(LdaSmi), U8(1),
-  /*   76 E> */ B(Add), R(0),
+  /*   76 E> */ B(AddSmi), U8(1), R(0),
                 B(Star), R(4),
                 B(LdaSmi), U8(2),
                 B(Star), R(1),
   /*   88 E> */ B(Mul), R(4),
                 B(Add), R(3),
                 B(Star), R(2),
                 B(LdaSmi), U8(3),
                 B(Star), R(1),
   /*   98 E> */ B(Add), R(2),
                 B(Star), R(3),
@@ skipping 43 matching lines @@
                 B(Inc),
                 B(Star), R(0),
   /*   72 E> */ B(Add), R(3),
   /*   76 S> */ B(Return),
 ]
 constant pool: [
 ]
 handlers: [
 ]