Add RFC2047-compliant MIME text decoder #22865

Job	Run time
Core running from src / Linux	2m 16s
Core running from build / MacOS	3m 22s
Core running from build / Windows	4m 51s
Core running from src / MacOS	4m 24s
Core running from build / Linux	2m 48s
Core running from src / Windows	3m 55s
Gutenberg running from build / MacOS	12m 45s
Gutenberg running from src / Linux	8m 53s
Gutenberg running from build / Linux	8m 23s
Gutenberg running from src / MacOS	15m 44s
Gutenberg running from build / Windows	13m 34s
Gutenberg running from src / Windows	12m 59s
Slack Notifications	-1s
Failed workflow tasks	-1s
	1h 33m 52s

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