Subshells implemented using tornado event loops on 6.x branch #3332

Job	Run time
build (ubuntu-latest, 3.9)	5m 13s
check_release	1m 48s
build (ubuntu-latest, 3.13)	5m 3s
build (windows-latest, 3.9)	9m 0s
test_docs	36s
build (windows-latest, 3.13)	7m 33s
build (macos-latest, 3.9)	4m 56s
build (macos-latest, 3.13)	4m 44s
Test Lint	54s
build (ubuntu-latest, pypy-3.9)	7m 45s
build (macos-latest, 3.10)	4m 46s
Test Minimum Versions	2m 27s
build (ubuntu-latest, 3.11)	4m 40s
Test Prereleases	3m 49s
build (ubuntu-latest, 3.12)	5m 45s
test_without_debugpy (ubuntu-latest, 3.9)	2m 16s
link_check	4m 1s
Make SDist	22s
Install from SDist and Test	2m 12s
coverage	0s
	1h 17m 50s

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