add(gha): test Python versions and update docs

[k-dovgan]

This workflow is added for illustrative purposes, for easy checking different Python versions compatibility with current Universum or potential changes. It can be run manually on demand, and is advised to be checked for any new Universum release.

[github-actions]

Test Results

713 tests  ±0   709 ✅ ±0   22m 17s ⏱️ + 1m 36s
  1 suites ±0     4 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit 05a0159. ± Comparison against base commit a26db3b.

♻️ This comment has been updated with latest results.

[github-actions]

Here is the summarized build result:
5. Executing build steps
5.1. [ 1/8 ] Create virtual environment - Success
5.2. [ 2/8 ] Update Docker images - Success
5.3. [ 3/8 ] Install Universum for tests - Success
5.4. [ 4/8 ] Make - Success
5.5. Collecting artifacts for the 'Make' step - Success
5.6. [ 5/8 ] Make tests - Success
5.7. Collecting artifacts for the 'Make tests' step - Success
5.8. [ 6/8 ] Collect test results - Success
5.9. Collecting artifacts for the 'Collect test results' step - Success
5.10. [ 7/8 ] Run static pylint - Success
5.11. [ 8/8 ] Run static type checker - Failed

Here is the link to Github Actions build: https://github.com/Samsung/Universum/actions/runs/25886892463

[k-dovgan]

Workflow example: https://github.com/Samsung/Universum/actions/runs/25885374074

[i-keliukh]

I see the workflow failed on "Setup Python" step for 3.6 and 3.7 and on making docker images for 3.8 and 3.9. The updated doc says that tests require Python >= 3.12. So it is not clear what is the reason of having 3.6-3.11 tested.
Another issue - the nox_only decorator is not updated. I think we should either change it or remove corresponding tests.

[k-dovgan]

I see the workflow failed on "Setup Python" step for 3.6 and 3.7 and on making docker images for 3.8 and 3.9. The updated doc says that tests require Python >= 3.12. So it is not clear what is the reason of having 3.6-3.11 tested.

I think I might add some kind of switch in tests between "under 3.12 - higher" in a different PR. I'd leave it as is now for active Python versions (3.10 and higher), as this WF is more illustrative, than "required": you can see I only left "workflow_dispatch" trigger, so it only can be run manually.

Another issue - the nox_only decorator is not updated. I think we should either change it or remove corresponding tests.

Same here: the decorator is not actually connected to nox, it's about regression. It is now used correctly, and it needs to be renamed — but as I see the tests need to be fixed in several places for Python other than 3.12, I'd leave it to the next PR.

[i-keliukh]

This WF is more illustrative, than "required": you can see I only left "workflow_dispatch" trigger, so it only can be run manually.

No problem. Please describe the purpose of the workflow in the PR description.