move data_structure_dicts, obsolete_variables and variable_metadata t…

[clmould]

…o process/core/data_structure

Description

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 49.87%. Comparing base (a6cc0e2) to head (eb4d654).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4562   +/-   ##
=======================================
  Coverage   49.87%   49.87%           
=======================================
  Files         151      151           
  Lines       29873    29873           
=======================================
  Hits        14899    14899           
  Misses      14974    14974           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.