Replace Tornado with AnyIO #1939

Job	Run time
build (ubuntu-latest, 3.8)	4m 43s
check_release	2m 34s
build (ubuntu-latest, 3.11)	2m 54s
build (windows-latest, 3.8)	7m 48s
test_docs	2m 51s
build (windows-latest, 3.11)	7m 2s
build (macos-latest, 3.8)	4m 58s
build (macos-latest, 3.11)	3m 26s
Test Lint	1m 5s
build (windows-latest, 3.9)	5m 25s
link_check	4m 12s
build (ubuntu-latest, pypy-3.8)	6m 6s
Make SDist	36s
build (macos-latest, 3.10)	4m 6s
Test Minimum Versions	4m 17s
Test Prereleases	2m 41s
test_without_debugpy (ubuntu-latest, 3.9)	1m 39s
Install from SDist and Test	1m 55s
coverage	0s
tests_check	9s
	1h 8m 27s

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