Add `GH_OST_INSTANT_DDL` for gh-ost-on-success hook #1363

Job	Run time
docker-tests (mysql:8.4.3)	10m 54s
docker-tests (percona/percona-server:8.0.41-32)	10m 15s
docker-tests (mysql:8.0.41)	11m 6s
docker-tests (mysql/mysql-server:5.7.41)	11m 37s
	43m 52s

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