WIP Use strong references to `gbm_device` in `Surface`/`BufferObject`

[ids1024]

Using a strong reference is the most obvious way to address https://github.com/Smithay/smithay/issues/1102. And getting rid of DeviceDestroyedError makes the API a fair bit cleaner.

Though Device.fd will also need to be reference counted for this to fix the issue here. Presumably. And this will need testing. Leaving as a draft at the moment.

Any reason not to do this, or why it may cause problems? I guess Device will require T: Sync...