There exists a method PowerSeries_poly.__floordiv__(), but it is not clear how it differs from ordinary division (see #15601 comment:43), or how it should differ mathematically.

We replace this method by a new method PowerSeries._floordiv_(), which returns the Euclidean quotient over fields and is a deprecated alias for _div_() over other rings.

CC: @jdemeyer

Component: algebra

Author: Peter Bruin

Branch/Commit: b7cd5cb

Reviewer: Bruno Grenet

Issue created by migration from https://trac.sagemath.org/ticket/20062