SystemMonitor: Add a devices tab

This tab combines info from /proc/devices with device file paths from /dev.

Applications/SystemMonitor/DevicesModel.h

@@ -0,0 +1,44 @@
+#pragma once
+
+#include <AK/AKString.h>
+#include <AK/Vector.h>
+#include <LibGUI/GModel.h>
+
+class DevicesModel final : public GModel {
+public:
+    enum Column {
+        Device = 0,
+        Major,
+        Minor,
+        ClassName,
+        Type,
+        __Count
+    };
+
+    virtual ~DevicesModel() override;
+    static NonnullRefPtr<DevicesModel> create();
+
+    virtual int row_count(const GModelIndex&) const override;
+    virtual int column_count(const GModelIndex&) const override;
+    virtual String column_name(int column) const override;
+    virtual ColumnMetadata column_metadata(int column) const override;
+    virtual GVariant data(const GModelIndex&, Role = Role::Display) const override;
+    virtual void update() override;
+
+private:
+    DevicesModel();
+
+    struct DeviceInfo {
+        String path;
+        unsigned major;
+        unsigned minor;
+        String class_name;
+        enum Type {
+            Block,
+            Character
+        };
+        Type type;
+    };
+
+    Vector<DeviceInfo> m_devices;
+};