Broke down sampler tests

.gitlab-ci.yml

test/core/prior/analytical_test.py

test/core/prior/base_test.py

test/core/prior/conditional_test.py

test/core/prior/dict_test.py

test/core/prior/interpolated_test.py

test/core/prior/joint_test.py

test/core/sampler/base_sampler_test.py

test/core/sampler/cpnest_test.py

test/core/sampler/dynamic_dynesty_test.py

test/core/sampler/dynesty_test.py

test/core/sampler/emcee_test.py

test/core/sampler/fake_sampler_test.py

test/core/sampler/kombine_test.py

test/core/sampler/nestle_test.py

test/core/sampler/polychord_test.py

test/core/sampler/proposal_test.py

test/core/sampler/ptemcee_test.py

test/core/sampler/ptmcmc_test.py

test/core/sampler/pymc3_test.py