LibWeb+WebContent: Move Serenity EventLoop and Font plugins into LibWeb

These are exactly what's wanted by headless-browser too, so this saves
us some duplication. LibWeb already links LibCore so it should not
cause any issues for Ladybird.

Userland/Libraries/LibWeb/Platform/TimerSerenity.cpp

@@ -0,0 +1,84 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "TimerSerenity.h"
+#include <AK/NonnullRefPtr.h>
+#include <LibCore/Timer.h>
+
+namespace Web::Platform {
+
+NonnullRefPtr<TimerSerenity> TimerSerenity::create()
+{
+    return adopt_ref(*new TimerSerenity);
+}
+
+TimerSerenity::TimerSerenity()
+    : m_timer(Core::Timer::construct())
+{
+    m_timer->on_timeout = [this] {
+        if (on_timeout)
+            on_timeout();
+    };
+}
+
+TimerSerenity::~TimerSerenity() = default;
+
+void TimerSerenity::start()
+{
+    m_timer->start();
+}
+
+void TimerSerenity::start(int interval_ms)
+{
+    m_timer->start(interval_ms);
+}
+
+void TimerSerenity::restart()
+{
+    m_timer->restart();
+}
+
+void TimerSerenity::restart(int interval_ms)
+{
+    m_timer->restart(interval_ms);
+}
+
+void TimerSerenity::stop()
+{
+    m_timer->stop();
+}
+
+void TimerSerenity::set_active(bool active)
+{
+    m_timer->set_active(active);
+}
+
+bool TimerSerenity::is_active() const
+{
+    return m_timer->is_active();
+}
+
+int TimerSerenity::interval() const
+{
+    return m_timer->interval();
+}
+
+void TimerSerenity::set_interval(int interval_ms)
+{
+    m_timer->set_interval(interval_ms);
+}
+
+bool TimerSerenity::is_single_shot() const
+{
+    return m_timer->is_single_shot();
+}
+
+void TimerSerenity::set_single_shot(bool single_shot)
+{
+    m_timer->set_single_shot(single_shot);
+}
+
+}