Ladybird/WebView: Move our PageClient to its own file

And rename it to PageClientLadybird while we're at it, it's not
"headless" by any means.

Ladybird/Utilities.cpp

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#define AK_DONT_REPLACE_STD
+
+#include "Utilities.h"
+
+AK::String akstring_from_qstring(QString const& qstring)
+{
+    return AK::String(qstring.toUtf8().data());
+}
+
+QString qstring_from_akstring(AK::String const& akstring)
+{
+    return QString::fromUtf8(akstring.characters(), akstring.length());
+}