Ladybird: Move Qt-specific classes and functions to a Qt subdirectory

This will help a lot with developing chromes for different UI frameworks
where we can see which helper classes and processes are really using Qt
vs just using it to get at helper data.

As a bonus, remove Qt dependency from WebDriver.

Ladybird/Qt/AudioCodecPluginQt.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Error.h>
+#include <AK/NonnullOwnPtr.h>
+#include <AK/NonnullRefPtr.h>
+#include <LibAudio/Forward.h>
+#include <LibWeb/Platform/AudioCodecPlugin.h>
+#include <QObject>
+
+namespace Ladybird {
+
+class AudioThread;
+
+class AudioCodecPluginQt final
+    : public QObject
+    , public Web::Platform::AudioCodecPlugin {
+    Q_OBJECT
+
+public:
+    static ErrorOr<NonnullOwnPtr<AudioCodecPluginQt>> create(NonnullRefPtr<Audio::Loader>);
+    virtual ~AudioCodecPluginQt() override;
+
+    virtual void resume_playback() override;
+    virtual void pause_playback() override;
+    virtual void set_volume(double) override;
+    virtual void seek(double) override;
+
+    virtual Duration duration() override;
+
+private:
+    explicit AudioCodecPluginQt(NonnullOwnPtr<AudioThread>);
+
+    NonnullOwnPtr<AudioThread> m_audio_thread;
+};
+
+}