fix(highs-model): use inclusive infinity bound checks

[kdheepak]

Resolves #104

[kdheepak]

with the following code:

import importlib.metadata

import pyoptinterface as poi
from pyoptinterface import highs

print("PyOptInterface:", importlib.metadata.version("pyoptinterface"))

for name, sense, objective_sense in (
    ("<=", poi.Leq, poi.ObjectiveSense.Minimize),
    (">=", poi.Geq, poi.ObjectiveSense.Maximize),
    ("==", poi.Eq, poi.ObjectiveSense.Minimize),
):
    model = highs.Model()
    # silent output from highs
    model.set_model_attribute(poi.ModelAttribute.Silent, True)

    x = model.add_variable(lb=0.0, ub=10.0)

    row = model.add_linear_constraint(x, sense, 1.0)

    model.set_objective(x, objective_sense)

    model.optimize()

    before = model.get_value(x)
    rhs_before = model.get_normalized_rhs(row)

    model.set_normalized_rhs(row, 2.0)

    model.optimize()

    after = model.get_value(x)
    rhs_after = model.get_normalized_rhs(row)

    print(
        f"{name}: rhs_before={rhs_before}, x_before={before}, rhs_after={rhs_after}, x_after={after}"
    )

Before this PR:

PyOptInterface: 0.6.1
<=: rhs_before=-inf, x_before=0.0, rhs_after=2.0, x_after=2.0
>=: rhs_before=1.0, x_before=10.0, rhs_after=2.0, x_after=2.0
==: rhs_before=1.0, x_before=1.0, rhs_after=2.0, x_after=2.0

After this PR and building locally:

PyOptInterface: 0.6.1
<=: rhs_before=1.0, x_before=0.0, rhs_after=2.0, x_after=0.0
>=: rhs_before=1.0, x_before=10.0, rhs_after=2.0, x_after=10.0
==: rhs_before=1.0, x_before=1.0, rhs_after=2.0, x_after=2.0