GLPK backend does not detect unboundedness in simplex-only mode #18838
Description
testcase:
sage: p = MixedIntegerLinearProgram(maximization=True, solver = "GLPK")
sage: p.set_objective(p[0])
sage: p.solver_parameter("simplex_or_intopt", "simplex_only")
sage: p.solve()
0.0
CC: @yuan-zhou @nathanncohen @dimpase @johnperry-math @dcoudert
Component: numerical
Author: Matthias Koeppe, Yuan Zhou
Branch/Commit: b8daa1f
Reviewer: Dima Pasechnik, David Coudert
Issue created by migration from https://trac.sagemath.org/ticket/18838