migration: Rename save_live_complete_precopy_thread to save_complete_precopy_thread

migration: Rename save_live_complete_precopy_thread to save_complete_precopy_thread

Recent patch [1] renames the save_live_complete_precopy handler to
save_complete, as the machine is not live in most cases when this
handler is executed. The same is true also for
save_live_complete_precopy_thread, therefore this patch removes the
"live" keyword from the handler itself and related types to keep the
naming unified.

In contrast to save_complete, this handler is only executed at the end
of precopy, therefore the "precopy" keyword is retained.

[1]: https://lore.kernel.org/all/20250613140801.474264-7-peterx@redhat.com/

Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Juraj Marcin <jmarcin@redhat.com>
Link: https://lore.kernel.org/r/20250626085235.294690-1-jmarcin@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>