Streamline Automatic Tests

[popescu-v]

Discard parallel tests, no longer relevant after the resource manager has been removed.
Group integration tests and remote-access tests into a separate, "integration-tests.yml", workflow that can only be launched manually.
Limit the number of Python versions to test: keep only the oldest (currently 3.10) and the newest (currently 3.14).
Consider what to do with the samples tests:

• only launch the "Iris"-based ones? (this does not include coclustering tests, though);
• change the samples to systematically use "Iris" where applicable? (this is a long effort, not clearly realizable without loss);
• group them with the integration tests, in the separate workflow (they are integration tests, after all, because they use the real Khiops core binaries).

If the last solution is chosen, then discard the "expensive tests" distinction (workflow input, Python decorator).

For this to work, also group all integration tests in a separate Python module, in separate unittest.TestCase classes. Thus, the Python library-only tests should be better separable from integration tests through adequate python -m unittest invocations.

The goal of this is to only test the Python library in "tests.yml", using fixtures and Khiops core mocks. All other tests, that do not do so, should be moved to the "integration-tests.yml" workflow.