Improve some tests to speed up the CI

[seisman]

Description of the desired feature

Here are the top slowest tests. Some may be improved to reduce the CI time.

4.64s call     tests/test_coast.py::test_coast_aliases[png]
3.28s call     tests/test_grdview.py::test_grdview_with_perspective_and_zaxis_frame[png]
2.28s call     gridops.py::pygmt.gridops.grdfilter
2.26s call     tests/test_coast.py::test_coast_world_mercator
1.98s call     tests/test_figure.py::test_shift_origin
1.74s call     tests/test_coast.py::test_coast_dcw_state[png]
1.74s call     src/inset.py::pygmt.src.inset.inset
1.73s call     tests/test_inset.py::test_inset_aliases[png]
1.66s call     tests/test_logo.py::test_logo_on_a_map[png]
1.65s call     tests/test_coast.py::test_coast_dcw_continent[png]
1.57s call     tests/test_plot.py::test_plot_from_file
1.55s call     tests/test_coast.py::test_coast_dcw_list[png]
1.51s call     tests/test_coast.py::test_coast_dcw_multiple[png]
1.50s call     tests/test_plot3d.py::test_plot3d_from_file[png]
1.49s call     tests/test_coast.py::test_coast_dcw_single[png]
1.49s call     tests/test_grdcontour.py::test_grdcontour_labels[png]
1.46s call     tests/test_coast.py::test_coast_iceland[png]
1.43s setup    tests/test_basemap.py::test_basemap
1.40s call     tests/test_grdimage.py::test_grdimage_shading_xarray[+a30+nt0.8-png]
1.38s call     tests/test_config.py::test_config
1.35s call     tests/test_grdimage.py::test_grdimage_shading_xarray[True-png]
1.19s call     tests/test_basemap.py::test_basemap_winkel_tripel
1.18s call     tests/test_coast.py::test_coast
1.13s call     tests/test_sphinx_gallery.py::test_pygmtscraper
1.11s call     tests/test_colorbar.py::test_colorbar_shading_float[png]
1.11s call     tests/test_colorbar.py::test_colorbar_shading_list[png]
1.11s call     tests/test_figure.py::test_figure_savefig_exists
1.11s call     tests/test_colorbar.py::test_colorbar_shading_string[png]
1.10s call     tests/test_colorbar.py::test_colorbar_shading_boolean[png]
1.08s call     tests/test_basemap.py::test_basemap_loglog
1.04s call     tests/test_grdcontour.py::test_grdcontour[png]
1.01s call     tests/test_grdimage.py::test_grdimage_central_meridians_and_standard_parallels[Q-180-30-png]
1.00s call     tests/test_grdimage.py::test_grdimage_central_meridians_and_standard_parallels[S-0-0-png]
1.00s call     tests/test_grdimage.py::test_grdimage_central_meridians_and_standard_parallels[S-180-0-png]
1.00s call     tests/test_grdimage.py::test_grdimage_central_meridians_and_standard_parallels[Q-123-30-png]
0.99s call     tests/test_text.py::test_text_varying_transparency[png]
0.99s call     tests/test_grdimage.py::test_grdimage_central_meridians_and_standard_parallels[S-123-30-png]
0.99s call     tests/test_grdimage.py::test_grdimage_central_meridians_and_standard_parallels[S-180-30-png]
0.99s call     tests/test_grdimage.py::test_grdimage_central_meridians_and_standard_parallels[S-123-0-png]
0.98s call     tests/test_grdimage.py::test_grdimage_central_meridians_and_standard_parallels[S-0-30-png]

Are you willing to help implement and maintain this feature? Yes/No

[seisman]

I'm closing this issue because we have refactored most tests recently, and the information in this PR is out-of-date.