Reduce testing time/memory

[f0uriest]

Running our basic unit tests now takes 1.5+ hrs for me locally, and fairly often it will get killed due to OOM issues if I'm trying to do anything else at the same time.

A few suggestions:

• Reduce resolution as much as possible wherever possible
• Drop resolution after doing desc.examples.get since in most cases we don't need all the detail
• for VMEC IO tests, make new baseline cases with like, 10 surfaces, since all we're testing is that things get loaded and saved correctly. We already know DESC and VMEC both work.
• See if we can eliminate some tests are are now redundant with others. There's ways to see which tests cover which lines, so we can cut tests that don't cover new ground: https://pytest-cov.readthedocs.io/en/latest/contexts.html