Use the OS upgrade's cancellable object for related operations

Instead of creating its own cancellable for operations related to the OS
upgrade, we should use the OS upgrade's own cancellable object.
This will allow e.g. to connect the cancellable object from outside the
update page's code.
1 job for wip/jrocha/use-upgrades-cancellable in 5 minutes and 16 seconds (queued for 4 seconds)
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passed #20106
build-gnome-software

00:05:16