Kernel: Rewrite whole device structure

We now have DevFileSystem which is derived from RamFileSystem. All
devices are RamInodes. We don't have separate DeviceManager anymore.
To iterate over devices, you can loop througn every inode in devfs.

kernel/kernel/FS/DevFS/FileSystem.cpp

@@ -0,0 +1,63 @@
+#include <BAN/ScopeGuard.h>
+#include <kernel/FS/DevFS/FileSystem.h>
+#include <kernel/FS/RamFS/Inode.h>
+#include <kernel/LockGuard.h>
+#include <kernel/Process.h>
+
+namespace Kernel
+{
+
+	static DevFileSystem* s_instance = nullptr;
+
+	void DevFileSystem::initialize()
+	{
+		ASSERT(s_instance == nullptr);
+		s_instance = new DevFileSystem(1024 * 1024);
+		ASSERT(s_instance);
+
+		auto root_inode = MUST(RamDirectoryInode::create(*s_instance, 0, Inode::Mode::IFDIR | 0755, 0, 0));
+		MUST(s_instance->set_root_inode(root_inode));
+	}
+
+	DevFileSystem& DevFileSystem::get()
+	{
+		ASSERT(s_instance);
+		return *s_instance;
+	}
+
+	void DevFileSystem::initialize_device_updater()
+	{
+		Process::create_kernel(
+			[](void*)
+			{
+				while (true)
+				{
+					s_instance->m_device_lock.lock();
+					s_instance->for_each_inode(
+						[](BAN::RefPtr<RamInode> inode)
+						{
+							if (inode->is_device())
+								((Device*)inode.ptr())->update();
+						}
+					);
+					s_instance->m_device_lock.unlock();
+
+					PIT::sleep(1);
+				}
+			}, nullptr
+		);
+	}
+
+	void DevFileSystem::add_device(BAN::StringView path, BAN::RefPtr<Device> device)
+	{
+		ASSERT(!path.contains('/'));
+		MUST(reinterpret_cast<RamDirectoryInode*>(root_inode().ptr())->add_inode(path, device));
+	}
+
+	dev_t DevFileSystem::get_next_rdev()
+	{
+		static dev_t next_rdev = 1;
+		return next_rdev++;
+	}
+
+}