Move example output to example_results

[reneSchm]

Motivation / Current Behaviour

Some examples create output files in the directory they are executed in. When using VSCode, this is the build/bin directory, making the files hard to find as well as cluttering the build directory with unrelated files.

Enhancement description

Change examples so that they create files inside memilio/example_results/, by using e.g.

const std::string result_dir = mio::path_join(mio::base_dir(), "example_results");

This way the output of the examples is predictable, and more visible. We may want to add that path to the .gitignore.

Additional context

The examples ode_secir_parameter_study.cpp and abm_parameter_study.cpp already do this.

Checklist

• Attached labels, especially loc:: or model:: labels.
• Linked to project