Kernel: Move all Graphics-related code into Devices/GPU directory

Like the HID, Audio and Storage subsystem, the Graphics subsystem (which
handles GPUs technically) exposes unix device files (typically in /dev).
To ensure consistency across the repository, move all related files to a
new directory under Kernel/Devices called "GPU".

Also remove the redundant "GPU" word from the VirtIO driver directory,
and the word "Graphics" from GraphicsManagement.{h,cpp} filenames.

Kernel/Devices/GPU/Intel/Plane/G33DisplayPlane.h

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/RefPtr.h>
+#include <AK/Try.h>
+#include <AK/Types.h>
+#include <Kernel/Devices/GPU/Intel/Plane/DisplayPlane.h>
+
+namespace Kernel {
+
+class IntelDisplayConnectorGroup;
+class IntelG33DisplayPlane final : public IntelDisplayPlane {
+public:
+    static ErrorOr<NonnullOwnPtr<IntelG33DisplayPlane>> create_with_physical_address(PhysicalAddress plane_registers_start_address);
+
+    virtual ErrorOr<void> enable(Badge<IntelDisplayConnectorGroup>) override;
+
+private:
+    explicit IntelG33DisplayPlane(Memory::TypedMapping<volatile IntelDisplayPlane::PlaneRegisters> plane_registers_mapping);
+};
+}