[Interpreter] Add a simple dead-code elimination bytecode optimizer.

test/cctest/interpreter/bytecode_expectations/DoExpression.golden

 #
 # Autogenerated by generate-bytecode-expectations.
 #
 
 ---
 pool type: string
 execute: yes
 wrap: yes
 do expressions: yes
 
@@ skipping 36 matching lines @@
 ]
 handlers: [
 ]
 
 ---
 snippet: "
   while(true) { var a = 10; a = do { ++a; break; }; a = 20; }
 "
 frame size: 2
 parameter count: 1
-bytecode array length: 24
+bytecode array length: 17
 bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   34 E> */ B(StackCheck),
   /*   56 S> */ B(LdaSmi), U8(10),
                 B(Star), R(1),
   /*   69 S> */ B(Inc),
                 B(Star), R(1),
                 B(Star), R(0),
-  /*   74 S> */ B(Jump), U8(11),
-                B(Mov), R(0), R(1),
-  /*   84 S> */ B(LdaSmi), U8(20),
-                B(Star), R(1),
-                B(Jump), U8(-19),
+  /*   74 S> */ B(Jump), U8(4),
+                B(Jump), U8(-12),
                 B(LdaUndefined),
   /*   94 S> */ B(Return),
 ]
 constant pool: [
 ]
 handlers: [
 ]