more robust conversion to pyarrow for output #706

Job	Run time
linux-64-py3.10	5m 5s
prototype_mtc	50m 51s
prototype_mtc	48m 46s
estimation_mode_test	16m 3s
placeholder_psrc	40m 13s
macOS	7m 22s
prototype_psrc_in_development	3m 39s
prototype_marin	1m 30s
win-64	10m 41s
prototype_mtc_extended	3h 12m 58s
random_seed_generation_test	2m 17s
placeholder_sandag	2h 24m 3s
develop-docbuild	0s
prototype_sandag_xborder	5m 25s
production_semcog	5m 19s
prototype_mwcog	48m 55s
placeholder_multiple_zone	7m 38s
	9h 50m 45s

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