update NonlinearSolver trait so that `solve_in_place` takes a `VectorViewMut` rather than a `&mut Vector`

[martinjrobins]

as per title, see https://docs.rs/diffsol/latest/diffsol/nonlinear_solver/trait.NonLinearSolver.html#tymethod.solve_in_place

This would allow the solvers to directly do the solve in each column of the diff matrix, which would mean that the old_state does not need to be stored, a significant storage reduction for the bdf and sdirk solvers

[martinjrobins]

sigh, I think this requires #47, since this arg gets passed to the nonlinear function https://docs.rs/diffsol/latest/src/diffsol/nonlinear_solver/newton.rs.html#17. #47 is a big breaking change though, so I'm not sure if I want to do that.