Kernel: Introduce a new graphics subsystem

This new subsystem is replacing the old code that was used to
create device nodes of framebuffer devices in /dev.

This subsystem includes for now 3 roles:
1. GraphicsManagement singleton object that is used in the boot
process to enumerate and initialize display devices.
2. GraphicsDevice(s) that are used to control the display adapter.
3. FramebufferDevice(s) that are used to control the device node in
/dev.

For now, we support the Bochs display adapter and any other
generic VGA compatible adapter that was configured by the boot
loader to a known and fixed resolution.

Two improvements in the Bochs display adapter code are that
we can support native bochs-display device (this device doesn't
expose any VGA capabilities) and also that we use the MMIO region,
to configure the device, instead of setting IO ports for such tasks.

Kernel/Graphics/GraphicsDevice.h

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2021, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/String.h>
+#include <AK/Types.h>
+#include <Kernel/Devices/BlockDevice.h>
+#include <Kernel/Graphics/FramebufferDevice.h>
+#include <Kernel/PhysicalAddress.h>
+
+namespace Kernel {
+class FramebufferDevice;
+class GraphicsDevice : public RefCounted<GraphicsDevice> {
+public:
+    enum class Type {
+        VGACompatible,
+        Bochs,
+        SVGA,
+        Raw
+    };
+    virtual ~GraphicsDevice() = default;
+    virtual void initialize_framebuffer_devices() = 0;
+    virtual Type type() const = 0;
+
+protected:
+    GraphicsDevice() = default;
+};
+
+}