Add support for `IMG` tags with `fetchpriority=low` or `fetchpriority=auto` #33207

Job	Run time
Determine Matrix	4s
Single Site Memcached / Test before	1m 42s
Multisite Default / Test current	1m 43s
Multisite Default / Test before	1m 43s
Multisite Memcached / Test before	1m 42s
Single Site Default / Test current	1m 42s
Multisite Memcached / Test current	1m 42s
Single Site Memcached / Test current	1m 42s
Single Site Default / Test before	1m 43s
matrix.label	0s
Slack Notifications	0s
Failed workflow tasks	1s
	13m 44s

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