Restructure tests part 2

.coveragerc

.gitlab-ci.yml

bilby/core/prior/base.py

bilby/gw/utils.py

setup.cfg

test/core/example_test.py

test/core/grid_test.py

test/core/likelihood_test.py

test/core/prior/base_test.py

test/core/prior/dict_test.py

test/core/prior/prior_test.py

test/core/result_test.py

test/core/sampler/sampler_run_test.py

test/core/series_test.py

test/core/utils_test.py

test/gw/conversion_test.py

test/gw/cosmology_test.py

test/gw/eos/eos_test.py

test/gw/likelihood_test.py

test/gw/plot_test.py