Create mini packages for python-based solvers

[BenjaminRodenberg]

@fsimonis proposed creating packages for the python-based solvers. See https://github.com/precice/tutorials/issues/547#issuecomment-2333343306.

I would suggest to do this as a follow-up step when https://github.com/precice/tutorials/pull/563 is complete.

[fsimonis]

Example of separate single-file solvers https://github.com/precice/tutorials/pull/600