LibJS/Bytecode: Don't reparse regular expressions on instantiation

The RegExpLiteral AST node already has the parsed regex::Parser::Result
so let's plumb that over to the bytecode executable instead of reparsing
the regex every time NewRegExp is executed.

~12% speed-up on language/literals/regexp/S7.8.5_A2.1_T2.js in test262.

Userland/Libraries/LibJS/Bytecode/RegexTable.h

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2023, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/DeprecatedString.h>
+#include <AK/DistinctNumeric.h>
+#include <AK/Vector.h>
+#include <LibRegex/RegexParser.h>
+
+namespace JS::Bytecode {
+
+AK_TYPEDEF_DISTINCT_NUMERIC_GENERAL(size_t, RegexTableIndex, Comparison);
+
+struct ParsedRegex {
+    regex::Parser::Result regex;
+    DeprecatedString pattern;
+    regex::RegexOptions<ECMAScriptFlags> flags;
+};
+
+class RegexTable {
+    AK_MAKE_NONMOVABLE(RegexTable);
+    AK_MAKE_NONCOPYABLE(RegexTable);
+
+public:
+    RegexTable() = default;
+
+    RegexTableIndex insert(ParsedRegex);
+    ParsedRegex const& get(RegexTableIndex) const;
+    void dump() const;
+    bool is_empty() const { return m_regexes.is_empty(); }
+
+private:
+    Vector<ParsedRegex> m_regexes;
+};
+
+}