Support trivial constraints in SCIP interfaces

[william-xue]

Fixes #3976.

Summary/Motivation:

Constraint.Feasible and Constraint.Infeasible are represented by TrivialRelationalExpression. The SCIP expression visitor dispatches on exact types, so both the direct and persistent interfaces currently raise NotImplementedError while compiling these constraints.

Changes proposed in this PR:

• Translate a trivial relation into a symbolic zero-degree PySCIPOpt expression, rather than letting Python reduce the constant inequality to a bool. This preserves Feasible as 0 <= 0 and Infeasible as 1 <= 0.
• Add direct and persistent interface regressions using min x, 0 <= x <= 1: the feasible case has known optimum x = 0, while adding Constraint.Infeasible must produce provenInfeasible with no solution.

Validation:

• .venv/bin/pytest -q --solver=scip_direct pyomo/contrib/solver/tests/solvers/test_scip_direct.py — 22 passed
• .venv/bin/pytest -q --solver=scip_persistent pyomo/contrib/solver/tests/solvers/test_scip_persistent.py — 18 passed
• .venv/bin/black --check pyomo/contrib/solver/solvers/scip/base.py pyomo/contrib/solver/tests/solvers/test_scip_direct.py pyomo/contrib/solver/tests/solvers/test_scip_persistent.py — unchanged

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