Bound urllib3<2 for consistent CPython3.X behaviour

[nenb]

Description

This addresses some bugs that I introduced described in #1060.

Bug 1: I didn't give a test_ prefix to the AI API test modules and so they weren't picked up by pytest. This has been addressed by a simple rename.
Bug 2: I didn't deal with the case where there was no Cohere API key present (as will be the case on the test runners). This has been addressed by some simple monkey patching.
Bug 3: The tests were failing for CPython 3.11, as documented in #1060. This fix was a bit more complicated. Ultimately it relates to the fact that vcrpy uses different versions of urllib3 depending on the CPython version, and that the different urllib3 versions have some unexpected changed behaviour that appears to not have an obvious fix. My solution in this PR was to only using urllib3<2 for the tests. I'm not aware of any other easy solutions. Hopefully this is okay.

Along the way I noted a more serious issue - at the moment you have tests disabled from your CI. This appears to be related to some changes to the Makefile that were introduced last week. Fixing this is not within the scope of this PR. @fnikolai

Related Issues

#1060

Checklist

• Is this code covered by new or existing unit tests or integration tests?
• Did you run make test successfully?
• Do new classes, functions, methods and parameters all have docstrings?
• Were existing docstrings updated, if necessary?
• Was external documentation updated, if necessary?

Additional Notes or Comments