(from #33752)

We lift the conversion code that sends symbolic and AA elements to a suitable embedded number field and back from the backend normaliz and create a new backend number_field, which just runs backend field on the converted number field elements.

This results in rather general (but slow) polyhedral code for algebraic data in pure Python.

Depends on #34195

CC: @yuan-zhou @kliem @jplab @videlec @tscrim

Component: geometry

Author: Matthias Koeppe, Yuan Zhou

Branch/Commit: c729884

Reviewer: Matthias Koeppe, Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/34479