sundials4py: expose SuperLUMT SUNLinearSolver in Python interfaces

[Copilot]

Expose SUNLinSol_SuperLUMT in sundials4py.core when SuperLU_MT is enabled, including constructor and ordering API surface. The change is fully gated so builds without SuperLU_MT remain unaffected.

• Binding surface

  • Added sunlinsol_superlumt binding unit and generated header.
  • Exported SUNLinSol_SuperLUMT(...) and SUNLinSol_SuperLUMTSetOrdering(...).

• Module registration

  • Registered SuperLUMT bindings in sundials4py.cpp under SUNDIALS_SUPERLUMT_ENABLED.

• Build wiring

  • Added conditional source inclusion and link dependency in bindings/sundials4py/CMakeLists.txt under SUNDIALS_ENABLE_SUPERLUMT.
  • Extended bindings/sundials4py/sunlinsol/generate.yaml with sunlinsol_superlumt.

• Python API coverage

  • Added a sunlinearsolver test path that conditionally exercises SuperLUMT creation when present.

from sundials4py.core import SUNLinSol_SuperLUMT, SUNLinSol_SuperLUMTSetOrdering

LS = SUNLinSol_SuperLUMT(y, A, num_threads=1, sunctx=sunctx)
SUNLinSol_SuperLUMTSetOrdering(LS, ordering_choice)