Kernel/Devices: Remove required_mode and device_name methods

These methods are no longer needed because SystemServer is able to
populate the DevFS on its own.

Device absolute_path no longer assume a path to the /dev location,
because it really should not assume any path to a Device node.

Because StorageManagement still needs to know the storage name, we
declare a virtual method only for StorageDevices to override, but this
technique should really be removed later on.

Kernel/TTY/VirtualConsole.h

@@ -107,9 +107,6 @@ private:
     // ^CharacterDevice
     virtual StringView class_name() const override { return "VirtualConsole"; }
 
-    // ^Device
-    virtual String device_name() const override;
-
     void set_active(bool);
     void flush_dirty_lines();