HTML API: Make non-body fragment creation methods private. #12224

Job	Run time
Core running from build / Core running from build / Linux	2m 10s
Core running from src / Core running from src / Linux	1m 54s
Core running from build / Core running from build / Windows	4m 5s
Core running from src / Core running from src / Windows	3m 52s
Core running from build / Core running from build / MacOS	2m 32s
Core running from src / Core running from src / MacOS	2m 17s
Gutenberg running from build / Gutenberg running from build / Linux	8m 42s
Gutenberg running from src / Gutenberg running from src / Linux	8m 44s
Gutenberg running from build / Gutenberg running from build / Windows	11m 24s
Gutenberg running from build / Gutenberg running from build / MacOS	9m 26s
Gutenberg running from src / Gutenberg running from src / Windows	12m 0s
Gutenberg running from src / Gutenberg running from src / MacOS	11m 27s
Slack Notifications / Prepare notifications	5s
Slack Notifications / Success notifications	2s
Slack Notifications / Cancelled notifications	0s
Slack Notifications / Fixed notifications	0s
Slack Notifications / Failure notifications	0s
Failed workflow tasks	0s
	1h 18m 40s

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