Test against older glue versions and update bqplot tests

[Carifio24]

This PR makes a few updates to the test suite:

• Rename test_data to make_data in the tests for the bqplot exporters, so that pytest doesn't think that it's a test
• Add glue### testing environments to test glue-plotly against older minor versions of glue. Since our current pin is to glue-core>=1.13.1, there's no need to go back further than 1.13.*. This resolves #54. The solution here isn't the most elegant, but I'm not sure of another way to do this.
• Remove tests for Python < 3.8, since glue requires Python >= 3.8.

[Carifio24]

Hmm, this worked for me locally, but from the output of pip freeze in the CI we aren't pulling in the old versions of glue in these environments. Will investigate further.