Replace Tornado with AnyIO #1940

Job	Run time
build (ubuntu-latest, 3.8)	3m 43s
build (ubuntu-latest, 3.11)	3m 5s
build (windows-latest, 3.8)	8m 57s
check_release	2m 26s
test_docs	3m 35s
build (windows-latest, 3.11)	5m 20s
build (macos-latest, 3.8)	4m 47s
Test Lint	1m 8s
Test Minimum Versions	4m 13s
build (macos-latest, 3.11)	3m 40s
build (windows-latest, 3.9)	6m 52s
test_without_debugpy (ubuntu-latest, 3.9)	2m 5s
build (ubuntu-latest, pypy-3.8)	6m 6s
link_check	2m 39s
build (macos-latest, 3.10)	4m 26s
Make SDist	32s
Test Prereleases	2m 10s
Install from SDist and Test	2m 0s
coverage	0s
tests_check	2s
	1h 7m 46s

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