Add type annotations to table.py

[henrikmidtiby]

Overview: What does this pull request change?

This PR adds type annotations to table.py.

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested

[behackl]

I pushed a reviewer commit reverting these parameters to Iterable. Sequence excludes NumPy arrays at type-checking time, even though arrays are documented and supported table inputs.

The constructor now materializes the outer and inner iterables immediately, so Iterable accurately reflects what the implementation requires while also safely supporting generators. I added regression coverage for iterable data, NumPy label arrays, and empty label iterables.

Happy to merge this now; thanks!