Swap out `db-type` and `db-version` for a more explicit `db-image` #2484

Job	Run time
Single site report / PHP 8.3 with mysql:8.4	1m 46s
Multisite report / PHP 8.3 with mysql:8.4 multisite	1m 32s
Slack Notifications	0s
Failed workflow tasks	0s
	3m 18s

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