Most code that looks for a regular collection id set on the remote is
removed, as these should never happen in flatpak repo setups now.
Some is replaces with looking at xa.sideload-collection-id:
* The libflatpak FlatpakRef::collection-id property now comes comes from the sideload id
* Various CLI commands showing or changing the collection-id for a remote now uses the sideload id
* Collection id deploy in update now sets the sideload-collection-id instead
* Setting the collection id for a remote in libflatpak now sets the sideload id
Additionally we now delete the code that allows unsigned summaries
when there is a collection id (because there is none).
create-usb now uses the sideload id as as collection id source when exporting.
The direct repo operations (export, bundle, commit-from) still support
collection ids, because on the server we do want to set it so that we
can sideload.
124b0be92e