Build: Improve Gutenberg integration workflow. #24202

Job	Run time
Core running from src / MacOS	3m 45s
Core running from src / Linux	2m 41s
Core running from src / Windows	5m 45s
Core running from build / MacOS	3m 47s
Core running from build / Linux	2m 53s
Core running from build / Windows	4m 36s
Slack Notifications / Prepare notifications	5s
Slack Notifications / Success notifications	3s
Slack Notifications / Failure notifications	0s
Slack Notifications / Cancelled notifications	0s
Slack Notifications / Fixed notifications	-1s
Failed workflow tasks	0s
	23m 34s

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