Do not hold Python's GIL when running commands #3142

Job	Run time
codecheck / codecheck	43m 33s
conda / conda (ubuntu-20.04)	11m 42s
docker / docker (fedora39)	20m 2s
conda / conda (macos-12)	12m 45s
docker / docker (rocky8)	22m 29s
mac / macports (macos-12)	17m 21s
conda / conda (macos-14)	4m 45s
mac / macports (macos-14)	2m 31s
linux / linux (-doc-mpi-)	40m 1s
mac / macports (+allmodules, macos-12)	22m 36s
mac / macsimple (macos-12)	9m 53s
linux / linux (-mpi-)	51m 26s
mac / macsimple (macos-14)	4m 57s
linux / linux (-coverage-mpi-)	1h 1m 47s
linux / linux (-debug-)	29m 11s
linux / linux (-debug-mpi-)	42m 24s
linux / linux (-intel-)	47m 7s
linux / linux (-pycv-mpi-)	18m 21s
linux / linux (-nvhpc-mpi-)	54m 12s
	8h 37m 3s

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