use yield from in poset code

<div id="comment:0"></div>

and other details in the Hasse diagrams

CC:  @tscrim

Component: **combinatorics**

Author: **Frédéric Chapoton**

Branch/Commit: **[`cd063f3`](https://github.com/sagemath/sagetrac-mirror/commit/cd063f3c8edae35f7df63126c5a1c71e694ea7eb)**

Reviewer: **Travis Scrimshaw**

_Issue created by migration from https://trac.sagemath.org/ticket/29857_

