TOP-986: Reorganize tests in preparation for FAT
This reorganizes the tests
folder to group tests similar to how they are grouped in JAMA: per milestone. This makes it easy for us to only run the AA0.5 tests for instance, by invoking pytest tests/aa05
. Plus, it allows us to set up fixtures for each milestone, since the AA0.5 tests will probably use different settings than later milestones.