It's a bit easier and more convenient to free and reload a List,
compared to a plain array. This will be helpful when allowing catalogs
to contain composite types.

Author: Justin Pryzby
Reviewed-by: Dean Rasheed, Tomas Vondra
Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com