Test using real EO data and other EO modalities

[vdplasthijs]

Currently data-dependent tests can only be run using --use-mock flag (which generates some mock csv data). It would be nice to facilitate (local) tests on a (subset) of real data too.

Currently, only (mock) coordinate data is implemented as EO modality for tests. We also need at least 1 image based mock (and real) source to tests some functionality such as image encoders.

Minor note; once the tests for encoders are more comprehensive, some (commented out) asserts can be moved from main files to tests.

[vdplasthijs]

Also note that test_yield_africa.py uses mock data but without the --use-mock flag. @robknapen

[vdplasthijs]

Fairly urgent because we're not testing the forward pass of geo encoders other than geoclip (see #70 )

[robknapen]

One of the recent PRs updated test_yield_africa.py wrt the --use-mock flag.