Python 3.14 compatibility

[jameswilburlewis]

PySPEDAS does not yet install cleanly under Python 3.14, due to an indirect dependency on pydantic-core, which does. not build cleanly under 3.14 yet. Once this is resolved, we should change quick_tests and possibly the full coverage suite to run under 3.14.

It will be interesting to see how 3.14 performs compared to 3.13. There was a big performance hit (15-20% slower?) going from 3.12 to 3.13 for our full coverage test, enough that the full coverage test could no longer complete within the 6 hour limit, so we had to go back to 3.12 for that suite.

[jameswilburlewis]

The pydantic-core issue on Python 3.14 seems to be resolved now, and the 'quick-tests' suite (which only tests the PySPEDAS core and not the extras [mth5, vires, maps]) passes. However, basemap doesn't build cleanly under Python 3.14, so the full coverage test fails. It may take quite some time for basemap to catch up, based on previous history.