migration: Add option to set postcopy-blocktime

Add a global property to allow enabling postcopy-blocktime feature.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20250613141217.474825-2-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>

migration/options.c

@@ -187,6 +187,8 @@ const Property migration_properties[] = {
     DEFINE_PROP_MIG_CAP("x-postcopy-ram", MIGRATION_CAPABILITY_POSTCOPY_RAM),
     DEFINE_PROP_MIG_CAP("x-postcopy-preempt",
                         MIGRATION_CAPABILITY_POSTCOPY_PREEMPT),
+    DEFINE_PROP_MIG_CAP("postcopy-blocktime",
+                        MIGRATION_CAPABILITY_POSTCOPY_BLOCKTIME),
     DEFINE_PROP_MIG_CAP("x-colo", MIGRATION_CAPABILITY_X_COLO),
     DEFINE_PROP_MIG_CAP("x-release-ram", MIGRATION_CAPABILITY_RELEASE_RAM),
     DEFINE_PROP_MIG_CAP("x-return-path", MIGRATION_CAPABILITY_RETURN_PATH),