faster pytest

[ddkohler]

pytest runs hundreds of tests, but handful of them take a disproportionately long time--this PR targets those methods, finding easy time saves that still preserves the purpose of the test (in most cases).

pytest time decreased by >50% through these changes.

Changes

• some from_COLORS tests are skipped due to long runtime
• reduce use of COLORS datasets in tests (time-consuming imports)
• chop, ichop, tests work with smaller datasets
• only test docs build on python 3.11, which is what we now use to build docs

Checklist

• updated CHANGELOG.md
• tests pass