sage.rings.infinity: Remove hard dependency on real_lazy and real_mpfi

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This is for **sagemath-polyhedra** (#32432).

CC:  @dimpase

Component: **refactoring**

Author: **Matthias Koeppe**

Branch/Commit: **[`fb9faa6`](https://github.com/sagemath/sagetrac-mirror/commit/fb9faa69e62b5af763c6116815eb01f6c6b8d255)**

Reviewer: **Dima Pasechnik**

_Issue created by migration from https://trac.sagemath.org/ticket/32778_

