General: Add speculative loading support via the Speculation Rules API. #14330

Job	Run time
Core running from build / Core running from build / Linux	2m 7s
Core running from src / Core running from src / Linux	2m 1s
Core running from build / Core running from build / Windows	3m 35s
Core running from src / Core running from src / Windows	3m 45s
Core running from build / Core running from build / MacOS	2m 29s
Core running from src / Core running from src / MacOS	2m 21s
Gutenberg running from build / Gutenberg running from build / Linux	8m 38s
Gutenberg running from src / Gutenberg running from src / Linux	8m 47s
Gutenberg running from build / Gutenberg running from build / Windows	12m 11s
Gutenberg running from src / Gutenberg running from src / Windows	11m 51s
Gutenberg running from build / Gutenberg running from build / MacOS	10m 8s
Gutenberg running from src / Gutenberg running from src / MacOS	9m 55s
Slack Notifications / Prepare notifications	3s
Slack Notifications / Success notifications	2s
Slack Notifications / Cancelled notifications	0s
Slack Notifications / Failure notifications	0s
Slack Notifications / Fixed notifications	0s
Failed workflow tasks	0s
	1h 17m 53s

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