LibRegex: Add a basic optimization pass

This currently tries to convert forking loops to atomic groups, and
unify the left side of alternations.

Userland/Libraries/LibRegex/RegexBytecodeStreamOptimizer.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include "Forward.h"
+
+namespace regex {
+
+class Optimizer {
+public:
+    static void append_alternation(ByteCode& target, ByteCode& left, ByteCode& right);
+};
+
+}