[DF] Make dataframe/test/CMakeLists.txt more readable
[DF] Make dataframe/test/CMakeLists.txt more readable

Add comments clarifying what the different test categories are.

olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root