Kernel: Introduce global variables and stats in /sys/kernel directory

The ProcFS is an utter mess currently, so let's start move things that
are not related to processes-info. To ensure it's done in a sane manner,
we start by duplicating all /proc/ global nodes to the /sys/kernel/
directory, then we will move Userland to use the new directory so the
old directory nodes can be removed from the /proc directory.

Kernel/FileSystem/SysFS/Subsystems/Kernel/MemoryStatus.h

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+#include <Kernel/FileSystem/SysFS/Subsystems/Kernel/GlobalInformation.h>
+#include <Kernel/KBufferBuilder.h>
+#include <Kernel/Library/LockRefPtr.h>
+#include <Kernel/UserOrKernelBuffer.h>
+
+namespace Kernel {
+
+class SysFSMemoryStatus final : public SysFSGlobalInformation {
+public:
+    virtual StringView name() const override { return "memstat"sv; }
+
+    static NonnullLockRefPtr<SysFSMemoryStatus> must_create(SysFSDirectory const& parent_directory);
+
+private:
+    explicit SysFSMemoryStatus(SysFSDirectory const& parent_directory);
+    virtual ErrorOr<void> try_generate(KBufferBuilder& builder) override;
+};
+
+}