[stable27] Move oc_file_metadata.metadata migration to a background job

[artonge]

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Fix https://github.com/nextcloud/server/issues/43571

nc_reset_instance server1 stable26 -o -c v26.0.0 cp ~/Pictures/Wallpapers/* ./data/admin/files/ occ files:scan admin occ files:scan admin --generate-metadata git add .htaccess git reset --hard mysql --password=password -u nextcloud_server1 -e "SELECT * FROM oc_file_metadata;" nextcloud_server1 nc_reset_instance server1 stable27 -u -o -c artonge/fix/metdata_column_migration php ./cron.php mysql --password=password -u nextcloud_server1 -e "SELECT * FROM oc_file_metadata;" nextcloud_server1