Follow-up from "Clean up xdg-foreign v2 wrappers"
The following discussion from !203 (merged) should be addressed:
A couple more issues to address:
- an imported resource should be created even if there is no specified exported surface with the provided handle, it's not a protocol error
- xdg_imported_v2.destroyed event is sent to wrong resource in zxdg_importer_v2_import_toplevel