Resolve "Create single class that handles `duration`, `sampling_frequency`, `start_time`, `frequency_array`, `time_array`, and maybe `frequency_domain_strain`, `time_domain_strain`"

This reverts commit e577ba98

PriorSet -> PriorDict
BBHPriorSet -> BBHPriorDict
BNSPriorSet -> BNSPriorDict
CalibrationPriorSet -> CalibrationPriorDict

Introduced backports with deprecation warnings for the old classes

1) Rename all tests to the pytest standard naming convention
2) Update to use pytest to run the tests and collect coverage
3) Simplify gitlab CI script using above changes