Include missing files in datastack; object-oriented datastack archiving

[emlys]

Description

This fixes #2589 by updating the datastack-archiving logic to include any file-based inputs referenced in a CSV, not just spatial inputs.

I also decided to refactor build_datastack_archive into an object-oriented design, where each Input type owns its method for archiving a value. I think this is overall clearer and more extensible than the previous design. In the case of the HRA criteria table, the custom archiving logic now lives in a HRACriteriaTableInput subclass.

Checklist

• Updated HISTORY.rst and link to any relevant issue (if these changes are user-facing)
• Updated the user's guide (if needed)
• Tested the Workbench UI (if relevant)

[emlys]

Moved these attributes into the base class because they are shared between Input and Output.