Replace some data files in cpp/tests

[reneSchm]

Motivation / Current Behaviour

There are several large data files in the cpp/tests, e.g. cpp/tests/data/pydata/District/vaccination_data.json, than can probably be replaced by generated data in the test that needs them.

The requirement for all these data files in tests/data may indicate that some functionality has too many hard coded requirements, such as file paths.

Enhancement description

Find out where the files are used and try to replace them, e.g. by moving the (reduced) data set to the test body, or by generating data. When necessary, extend or rewrite the interface of the tested class or function so that no file is required.

Additional context

#556 added a lot of data. Maybe it can be partially removed?

Checklist

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