feat: Move to Qubed as expansion primitive

[HCookie]

Description

Provide utility to get qubed from metadata, and use it to expand

• Update to Datatree in workflows

Note

If useful this code should be moved to earthkit-workflows

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

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📚 Documentation preview 📚: https://earthkit-workflows-anemoi--24.org.readthedocs.build/en/24/