[main] Copy `v21.0.0` release notes (#17097) #391

Job	Run time
Build and push lite (latest)	4m 9s
Build and push lite (percona80)	4m 21s
Build and push vttestserver (mysql80)	2m 38s
Build and push (bullseye, vtadmin)	1m 18s
Build and push (bullseye, vtorc)	37s
Build and push (bullseye, vtgate)	49s
Build and push (bullseye, vttablet)	50s
Build and push (bullseye, mysqlctld)	48s
Build and push (bullseye, mysqlctl)	56s
Build and push (bullseye, vtctl)	38s
Build and push (bullseye, vtctlclient)	38s
Build and push (bullseye, vtctld)	1m 35s
Build and push (bullseye, vtctldclient)	44s
Build and push (bullseye, logrotate)	20s
Build and push (bullseye, logtail)	24s
Build and push (bullseye, vtbackup)	46s
Build and push (bullseye, vtexplain)	47s
Build and push (bookworm, vtadmin)	1m 26s
Build and push (bookworm, vtorc)	40s
Build and push (bookworm, vtgate)	45s
Build and push (bookworm, vttablet)	44s
Build and push (bookworm, mysqlctld)	44s
Build and push (bookworm, mysqlctl)	49s
Build and push (bookworm, vtctl)	48s
Build and push (bookworm, vtctlclient)	54s
Build and push (bookworm, vtctld)	1m 38s
Build and push (bookworm, vtctldclient)	47s
Build and push (bookworm, logrotate)	26s
Build and push (bookworm, logtail)	39s
Build and push (bookworm, vtbackup)	49s
Build and push (bookworm, vtexplain)	1m 1s
Slack Notification if failed	0s
	34m 28s

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