Support external kernels #2274

Job	Run time
check_release	1m 14s
build (ubuntu-latest, 3.8)	6m 59s
build (ubuntu-latest, 3.11)	5m 38s
build (windows-latest, 3.8)	13m 49s
build (windows-latest, 3.11)	12m 23s
build (macos-latest, 3.8)	8m 39s
build (macos-latest, 3.11)	8m 58s
build (windows-latest, 3.9)	13m 47s
build (ubuntu-latest, pypy-3.8)	9m 27s
build (macos-latest, 3.10)	14m 17s
build (ubuntu-latest, 3.12)	6m 59s
Check Links	5m 44s
integration_check (ubuntu-latest, 3.8)	2m 47s
integration_check (ubuntu-latest, 3.9)	2m 36s
integration_check (ubuntu-latest, 3.10)	2m 31s
integration_check (ubuntu-latest, 3.11)	2m 24s
integration_check_pypy	1m 38s
Make SDist	42s
Test Docs	1m 46s
Test Examples	1m 4s
Test Lint	2m 15s
Test Minimum Versions	4m 38s
Test Prereleases	4m 30s
Install from SDist and Test	4m 3s
coverage	32s
tests_check	3s
	2h 19m 23s

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