LibJS/Bytecode: Add peephole optimization pass and fuse compare+jump

This patch adds a new "Peephole" pass for performing small, local
optimizations to bytecode.

We also introduce the first such optimization, fusing a sequence of
some comparison instruction FooCompare followed by a JumpIf into a
new set of JumpFooCompare instructions.

This gives a ~50% speed-up on the following microbenchmark:

    for (let i = 0; i < 10_000_000; ++i) {
    }

But more traditional benchmarks see a pretty sizable speed-up as well,
for example 15% on Kraken/ai-astar.js and 16% on Kraken/audio-dft.js :^)

Userland/Libraries/LibJS/Bytecode/Pass/GenerateCFG.cpp

@@ -63,6 +63,13 @@ static void generate_cfg_for_block(BasicBlock const& current_block, PassPipeline
             enter_label(true_target, current_block);
             return;
         }
+
+#define JS_ENUMERATE_FUSABLE_BINARY_OP(PreOp, ...) \
+    case Jump##PreOp:
+
+            JS_ENUMERATE_FUSABLE_BINARY_OPS(JS_ENUMERATE_FUSABLE_BINARY_OP)
+#undef JS_ENUMERATE_FUSABLE_BINARY_OP
+
         case JumpIf:
         case JumpNullish:
         case JumpUndefined: {