Use PARI's nfrootsof1() function to massively speed up zeta().

also fixes a bug that was not returning the empty list when all=True

CC: @pjbruin @yyyyx4 @roed314 @JohnCremona @kedlaya

Component: number fields

Author: Frédéric Chapoton

Branch/Commit: 09a9c1c

Reviewer: David Roe

Issue created by migration from https://trac.sagemath.org/ticket/18917