LibJS/Bytecode: Bring back the bytecode optimization pipeline

...minus the EliminateLoads pass, since it was not compatible with the
new bytecode format.

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

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Bytecode/PassManager.h>
+
+namespace JS::Bytecode::Passes {
+
+void DumpCFG::perform(PassPipelineExecutable& executable)
+{
+    started();
+
+    VERIFY(executable.cfg.has_value());
+    outln(m_file, "CFG Dump for {} basic blocks:", executable.executable.basic_blocks.size());
+    for (auto& entry : executable.cfg.value()) {
+        for (auto& value : entry.value)
+            outln(m_file, "{} -> {}", entry.key->name(), value->name());
+    }
+    outln(m_file);
+
+    finished();
+}
+
+}