Updates to workflow GUI layout and ordering

[ukmo-huw-lewis]

Contribution checklist

Aim to have all relevant checks ticked off before merging. See the developer's guide for more detail.

• Documentation has been updated to reflect change.
• New code has tests, and affected old tests have been updated.
• All tests and CI checks pass.
• Ensured the pull request title is descriptive.
• Ensure rose-suite.conf.example has been updated if new diagnostic added.
• Conda lock files have been updated if dependencies have changed.
• Attributed any Generative AI, such as GitHub Copilot, used in this PR.
• Marked the PR as ready to review.

[github-actions]

[ukmo-huw-lewis]

(left) Top-level structure before | (right) Proposed layout after change:

Main changes:

• brought Verification out to its own section rather than under 'Diagnostic options', assuming this is a panel that might evolve further. This change includes introducing a new verification metadata directory to reduce length of main file.
• Tidied sort keys so 'generic' surface, pressure, model level fields display first in list of Diagnostic options (not interrupted by Ensembles tab).
• Propose to then have Multi-variable, Ensembles and Q-Q plotting ahead of Derived diagnostics.

Derived diagnostics panel:

• Now listed in alphabetical order, and drawn "Convection" out from a "Precipitation" sub-category.
• Within each of the Derived diagnostic panels, introduced clearer sort-key templating. This forces some diagnostics into sorting by variable alphabetical order, then consistent '1, 2, 3' ordering on types of plot.
• Suggest review checks happy with ordering of options in each Derived diagnostics panel. I think they are sensible, but worth second opinion.

Should be possible to review proposed layout via local copy with
rose edit -C /home/users/huw.lewis/CSET/CSET/src/CSET/cset_workflow/

Ready for review.