Add CPA binding model

[AntoniaBerger]

This PR will add the CPA binding model by Briskot et al. (2021)

Todo:

• Implement Residual
• Implement Jacobin
• Enable rapid equilibrium
• Add tests to CI
• Add tests to verification
• Add documentation

Discussion points:

• How to handle pH?
• Support different AS functions in this model?

[jbreue16]

For the CI failing to build under windows: We've defined $\pi$ in a lot of functions and it should be optimzed away, i.e. inlined.
Since we agreed on making cpp20 the new standard for cadet-core, which will be mandatory anyways once #592 is merged, you could also use the following, which is possible with cpp20 upwards
#include <numbers> std::numbers::pi