We want to merge this when updating Smithay to have
https://github.com/Smithay/smithay/pull/1961, so that we don't panic the
the output/toplevel already has no strong references when the source is
created.
This doesn't change much, since the Smithay implementation is based on
the `cosmic-comp` version, but made more generic. We provide our own
implementation for our workspace capture protocol, but otherwise Smithay
handles the boilerplate now.
This should not cause any change in behavior.
