This ticket implements an edge view for graphs, as discussed in #22349 and in this message.

An edge view is a read-only iterable container of edges enabling operations like for e in E and e in E. In can be iterated multiple times. Checking membership is done in constant time. It avoids the construction of edge lists and so consumes little memory.

CC: @nthiery @sagetrac-tmonteil

Component: graph theory

Author: David Coudert

Branch/Commit: 3af5bba

Reviewer: Jeroen Demeyer, Vincent Delecroix, Frédéric Chapoton

Issue created by migration from https://trac.sagemath.org/ticket/27408