Dynamics of shape factor with Joule heating and thermal stratification on magnetohydrodynamic $${\mathbf{A}\mathbf{l}}_{2}{\mathbf{O}}_{3}-\mathbf{C}\mathbf{u}-\mathbf{T}\mathbf{i}{\mathbf{O}}_{2}/{\mathbf{H}}_{2}\mathbf{O}$$ nanofluid of stretching disk: an irreversibility analysis