gh-35135: `sage.geometry.integral_points`: Use generic impl if no `matrix_integer_dense`
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This is for the distribution sagemath-polyhedra (#32432) so that it does
not have to depend on the flint library.
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URL: https://github.com/sagemath/sage/pull/35135
Reported by: Matthias Köppe
Reviewer(s): Jonathan Kliem, Matthias Köppe
