Skip slow CI in nightly runs until failures can be debugged

[j-wags]

• Works around Scheduled CI failing #1997 by disabling slow tests, but leaves it open for future resolution

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.08%. Comparing base (74cfe94) to head (927278a).
Report is 2 commits behind head on main.

Additional details and impacted files

[mattwthompson]

If you haven't already considered it, the lowest-friction starting point might be to revert the relevant subset of #1970, i.e. move the Pytest config back to setup.cfg. But there have been some mysterious things going on in adjacent spaces so that might not fix it. (I'd love to see most of the slow tests go away altogether, but that's a bigger change)

[j-wags]

Thanks for the input. It would take me a while to tease apart #1970 into the minimal changes to revert to advance this, so my current thinking is to temporarily disable the slow tests so that nightlies regain some of their utility, and add a high-priority ticket to the backlog to debug and re-enable them.

[j-wags]

#2017 is a better solution