https://pari.math.u-bordeaux.fr/dochtml/html/General_number_fields.html#se:polredbest

and

https://pari.math.u-bordeaux.fr/dochtml/html/General_number_fields.html#se:polred

Depends on #20200

Component: number fields

Issue created by migration from https://trac.sagemath.org/ticket/22165