Remove lms.envs.test import from cms.envs.test #37348

Now with a shared openedx/envs/common.py settings module between the LMS and CMS, it is problematic to import settings across services. This can lead to settings with mutable values being inadvertently changed. A discussion on this issue can be found here.

The task is to refactor cms/envs/test.py to no longer import settings from lms/envs/test.py. This is to be done without changing the final rendered setting of the module. To ensure the refactoring doesn't alter the rendered settings, you can take a diff of the dump_settings command between your branch and the master branch and verify the settings are not rendered differently.

Once this is accomplished (and cms/envs/common.py does not import from lms/envs/common.py; link), we can remove the warning at the top of openedx/envs/common.py introduced in #37337.