Add/1034

[PGijsbers]

Turn on lazy loading by default for datasets.
Leaving tasks for a separate PR as I notice the diff is getting big since I made some additional changes to the tests.
So only progress for #1034.

I couldn't clean up everything, but I tried to clean things up a little bit.
The use of parametrize required me to work outside of the unittest class.
I tried to still make behavior similar as possible so its easier that they're not doing wildly different things (I do think that a lot of the setup/teardown that come with the general behavior isn't really needed though).

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.28%. Comparing base (1d707e6) to head (44dcb03).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@ Coverage Diff @@## develop #1352 +/- ##
===========================================
- Coverage 84.33% 84.28% -0.06% 
===========================================
Files 38 38 Lines 5293 5288 -5 ===========================================
- Hits 4464 4457 -7 - Misses 829 831 +2 

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[LennartPurucker]

LGTM; very nice refactor of the tests!

Otherwise, no further comments from my side.