Subshells implemented using tornado event loops on 6.x branch #3341

Job	Run time
check_release	1m 54s
build (ubuntu-latest, 3.9)	57s
test_docs	39s
Test Lint	1m 7s
build (ubuntu-latest, 3.13)	55s
Test Minimum Versions	1m 7s
build (windows-latest, 3.9)	3m 3s
test_without_debugpy (ubuntu-latest, 3.9)	50s
build (windows-latest, 3.13)	3m 4s
link_check	3m 13s
build (macos-latest, 3.9)	1m 11s
Make SDist	31s
build (macos-latest, 3.13)	48s
build (ubuntu-latest, pypy-3.9)	3m 8s
Test Prereleases	59s
build (macos-latest, 3.10)	1m 13s
build (ubuntu-latest, 3.11)	57s
build (ubuntu-latest, 3.12)	53s
Install from SDist and Test	47s
coverage	1s
	27m 17s

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