Part of #32191 (Meta-ticket: Audit/fix all uses of MixedIntegerLinearProgram in sage.combinat, sage.graphs).

We update the following in generic_graph.py

• flow
• multicommodity_flow
• disjoint_routed_paths
• edge_disjoint_paths
• vertex_disjoint_paths

and in graph.py:

• bounded_outdegree_orientation

Depends on #32197

CC: @mkoeppe @tscrim @dimpase

Component: graph theory

Author: David Coudert

Branch/Commit: 43c0d59

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/32248