Add operator-splitting test

This adds an operator splitting test implementing the fenics example about coupling of the Navier Stokes problem with a chemical reaction. From the dune-codegen point of view this tests:

• A more complex example of forms depending on additional coefficients
• Passing additional information to the coefficient as cargo
• More complex drive block generation

In addition in provides an example how operator splitting with driver blocks can look like.

Notes:

• This uses a msh that models the fenics problem with a flow around a cylinder. For the purpose of testing one could use a smaller grid. Instead I opted for only doing one time step.
• This only tests generation and compilation and not if the program is calculating the correct thing. This is impossible since we don't have an analytical solution.