PWG_common_production_run_json: Use POSIX complient builtin for python finding

Reasons: which command is different in Debian and in CentOS/RockyLinux (alias + extra options)
=> This lead to trouble when vae23/vae24 started with scrontab from bare-metal virgo3 (e.g. for Weekly tests)
=> Same if container/image started by hand with apptainer from bare-metal virgo3 (e.g. for dev container testing before custom mass jobs with SLURM)
=> command -v is the advised standard (especially on bash)
=> See also https://unix.stackexchange.com/a/85250

Redmine: Refs #3638

added Analysis BugFix CI/CD labels

requested review from @f.kornas

assigned to @f.uhlig

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Dear @f.uhlig, @p.-a.loizeau,

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merged