Refresh test infrastructure

[weaverba137]

This PR closes #798 by refreshing the test infrastructure.

[coveralls]

Coverage increased (+11.6%) to 56.294% when pulling dd577ce on refresh-tests into c5e89fa on main.

[weaverba137]

@geordie666, I think I found the answer: pytest>=7 and pytest-cov>=4 give lower coverage than pytest<7; pytest-cov<4 which is what we have at NERSC. I've pinned to those older versions, and the coverage value now matches the NERSC value.

desitarget/svX/svX_cuts.py is imported by importlib.import_module instead of a standard import statement, & this seems to be incompatible with how recent versions of pytest-cov counts coverage. Further research will be needed to fix this long-term, but for now pinning the versions works.

[geordie666]

Thanks @weaverba137, I appreciate you running carefully through some of these abstruse cases. This all looks good to me, so feel free to merge when you're ready.

FYI (in case you were thinking of tagging now that tests pass): I'll need to make a couple of updates in the next few days to run randoms for DR10 of the Legacy Surveys. I'll make a new tag when I've completed those updates.

[weaverba137]

I don't actually need to tag this immediately, so go ahead and tag based on your own changes when you're ready.