TST: Remove yield tests

[matthewturk]

To finish migrating to pytest we will need to eliminate all yield-tests.

Here is a list of places where yield shows up in a test_*.py file; not all are actual test files.

./tests/test_install_script.py
./doc/source/cookbook/tests/test_cookbook.py
./yt/tests/test_load_sample.py
./yt/tests/test_load_errors.py
./yt/visualization/tests/test_mesh_slices.py
./yt/visualization/tests/test_save.py
./yt/visualization/tests/test_callbacks.py
./yt/visualization/tests/test_particle_plot.py
./yt/visualization/tests/test_geo_projections.py
./yt/visualization/tests/test_plotwindow.py
./yt/visualization/tests/test_raw_field_slices.py
./yt/visualization/tests/test_line_plots.py
./yt/visualization/tests/test_profile_plots.py
./yt/visualization/volume_rendering/tests/test_vr_orientation.py
./yt/visualization/volume_rendering/tests/test_mesh_render.py
./yt/fields/tests/test_sph_fields.py
./yt/fields/tests/test_xray_fields.py
./yt/fields/tests/test_fields.py
./yt/frontends/owls_subfind/tests/test_outputs.py
./yt/frontends/ramses/tests/test_outputs_pytest.py
./yt/frontends/ramses/tests/test_outputs.py
./yt/frontends/arepo/tests/test_outputs.py
./yt/frontends/fits/tests/test_outputs.py
./yt/frontends/gdf/tests/test_outputs_nose.py
./yt/frontends/ahf/tests/test_outputs.py
./yt/frontends/gadget_fof/tests/test_outputs.py
./yt/frontends/gizmo/tests/test_outputs.py
./yt/frontends/owls/tests/test_outputs.py
./yt/frontends/moab/tests/test_c5.py
./yt/frontends/tipsy/tests/test_outputs.py
./yt/frontends/rockstar/tests/test_outputs.py
./yt/frontends/chombo/tests/test_outputs.py
./yt/frontends/nc4_cm1/tests/test_outputs.py
./yt/frontends/enzo/tests/test_outputs.py
./yt/frontends/ytdata/tests/test_old_outputs.py
./yt/frontends/ytdata/tests/test_outputs.py
./yt/frontends/gamer/tests/test_outputs.py
./yt/frontends/athena_pp/tests/test_outputs.py
./yt/frontends/exodus_ii/tests/test_outputs.py
./yt/frontends/athena/tests/test_outputs.py
./yt/frontends/art/tests/test_outputs.py
./yt/frontends/boxlib/tests/test_outputs.py
./yt/frontends/gadget/tests/test_outputs.py
./yt/frontends/artio/tests/test_outputs.py
./yt/frontends/amrvac/tests/test_units_override.py
./yt/frontends/amrvac/tests/test_outputs.py
./yt/frontends/flash/tests/test_outputs.py
./yt/frontends/enzo_e/tests/test_outputs.py
./yt/testing.py
./yt/data_objects/tests/test_connected_sets.py
./yt/data_objects/tests/test_particle_trajectories.py
./yt/geometry/tests/test_particle_octree.py
./yt/geometry/coordinates/tests/test_cylindrical_coordinates.py
./yt/geometry/coordinates/tests/test_spherical_coordinates.py
./yt/geometry/coordinates/tests/test_axial_pixelization.py
./yt/utilities/tests/test_config.py

[matthewturk]

I believe that this list is essentially broken into three bits:

• false positives, where yield is already inside a pytest fixture or something else
• places where we use answer test (specifically, a subclass of AnswerTestingTest ; see TST: Migrate to pytest-answer and pytest-mpl #3735 )
• places that can easily be fixed (like test_fields)