Add Conda-Forge Package Testing Workflow

[popescu-v]

The current .github/workflows/conda.yml workflow builds the Conda package in the CI of the repo, then tests the resulting build artifact.
However, this artifact is not guaranteed to be strictly identical to the package built and shipped on conda-forge, because the build infrastructure is different.
Hence, we need a separate workflow to retrieve the khiops Python package from conda-forge and test it in the current test matrix.

Consequently, we need to create a new .github/workflows/test-conda-forge-package.yml, which could start from a copy of .github/workflows/conda.yml, with the following changes:

1. drop the build job altogether;
2. drop the "Download Conda Package Artifact" of the test job;
3. Add supplemental khiops-version required input;
4. Make all the other inputs required and drop the DEFAULT_* environment variables;
5. edit the "Install the Khiops Conda package" step of the test job to simply install the relevant version (as per the khiops-version input) of the khiops package from conda-forge;
6. Drop the release job altogether.
7. Make the workflow launchable only manually, via workflow_dispatch.

[popescu-v]

To generalize (to the extent that is relevant!) to Khiops core and to the drivers.

[lucaurelien]

Core : Learning Test OK
Python : OK
Driver : Learning Test to be done