`shcemadiff`: support `INSTANT` DDL for changing column visibility #371

Job	Run time
Set push variable	1s
Build and push lite (latest)	2m 7s
Build and push vttestserver (mysql80)	1m 47s
Build and push lite (percona80)	2m 15s
Build and push (bullseye, vtadmin)	59s
Build and push (bullseye, vtorc)	41s
Build and push (bullseye, vtgate)	39s
Build and push (bullseye, vttablet)	44s
Build and push (bullseye, mysqlctld)	25s
Build and push (bullseye, mysqlctl)	40s
Build and push (bullseye, vtctl)	45s
Build and push (bullseye, vtctlclient)	40s
Build and push (bullseye, vtctld)	58s
Build and push (bullseye, vtctldclient)	48s
Build and push (bullseye, logrotate)	18s
Build and push (bullseye, logtail)	25s
Build and push (bullseye, vtbackup)	44s
Build and push (bullseye, vtexplain)	43s
Build and push (bookworm, vtadmin)	1m 5s
Build and push (bookworm, vtorc)	42s
Build and push (bookworm, vtgate)	45s
Build and push (bookworm, vttablet)	31s
Build and push (bookworm, mysqlctld)	47s
Build and push (bookworm, mysqlctl)	42s
Build and push (bookworm, vtctl)	43s
Build and push (bookworm, vtctlclient)	33s
Build and push (bookworm, vtctld)	1m 17s
Build and push (bookworm, vtctldclient)	38s
Build and push (bookworm, logrotate)	28s
Build and push (bookworm, logtail)	29s
Build and push (bookworm, vtbackup)	59s
Build and push (bookworm, vtexplain)	35s
	25m 53s

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