Run subset of tests in environment with no extras installed

See:

- #171

Our current testing scenario doesn't test for a case where a core module depends on a package defined as an extra. All packages that are extras should nest their imports and only be resolved at runtime.

_Originally posted by @cmungall in https://github.com/INCATools/ontology-access-kit/issues/743#issuecomment-2080292455_

Start by reading the referenced issue #171 and inspecting the repository's current testing setup. Add a test scenario that runs core-module tests with no optional extras installed, and verify that extra-package imports are deferred until runtime.

Written by the indexing model from the issue text.