The goal of this ticket is to make number fields work when the defining polynomial is not integral or not monic.

If the user specifies a non-integral or non-monic polynomial to define an absolute or relative number field, we define the corresponding PARI number field by a monic integral polynomial obtained from the PARI functions polredbest and rnfpolredbest, respectively.

The new methods NumberField_generic._pari_absolute_structure() and NumberField_relative._pari_relative_structure() return the data needed to convert elements between the Sage NumberField and the PARI nf structure.

Depends on #18740

CC: @katestange @sagetrac-Bouillaguet

Component: number fields

Author: Peter Bruin

Branch/Commit: 8b86c52

Reviewer: Kartik Venkatram

Issue created by migration from https://trac.sagemath.org/ticket/252