Do not hold Python's GIL when running commands #51

Job	Run time
codecheck / codecheck	43m 37s
docker / docker (fedora39)	20m 19s
docker / docker (rocky8)	23m 34s
linux / linux (-doc-mpi-)	39m 39s
linux / linux (-mpi-)	51m 40s
conda / conda (ubuntu-20.04)	11m 23s
linux / linux (-coverage-mpi-)	1h 5m 3s
conda / conda (macos-12)	5m 33s
mac / macports (macos-12)	18m 19s
linux / linux (-debug-)	30m 40s
conda / conda (macos-14)	1m 53s
mac / macsimple (macos-12)	11m 51s
mac / macports (macos-14)	2m 30s
mac / macsimple (macos-14)	5m 7s
linux / linux (-debug-mpi-)	41m 55s
mac / macports (+allmodules, macos-12)	26m 12s
linux / linux (-intel-)	47m 32s
linux / linux (-pycv-mpi-)	19m 49s
linux / linux (-nvhpc-mpi-)	56m 36s
	8h 43m 12s

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