Kernel/Devices: Defer creation of SysFS component after the constructor

Instead of doing so in the constructor, let's do immediately after the
constructor, so we can safely pass a reference of a Device, so the
SysFSDeviceComponent constructor can use that object to identify whether
it's a block device or a character device.
This allows to us to not hold a device in SysFSDeviceComponent with a
RefPtr.
Also, we also call the before_removing method in both SlavePTY::unref
and File::unref, so because Device has that method being overrided, it
can ensure the device is removed always cleanly.

Kernel/Devices/HID/HIDManagement.cpp

@@ -112,6 +112,7 @@ UNMAP_AFTER_INIT void HIDManagement::enumerate()
     m_i8042_controller->detect_devices();
     if (m_i8042_controller->mouse())
         m_hid_devices.append(m_i8042_controller->mouse().release_nonnull());
+
     if (m_i8042_controller->keyboard())
         m_hid_devices.append(m_i8042_controller->keyboard().release_nonnull());
 }