refactor: consolidate StorageOwnership to the generated StrEnum

[vdusek]

Summary

• Removes the duplicate StorageOwnership Literal from _types.py.
• Reuses the auto-generated StorageOwnership StrEnum from _models.py in the dataset, key-value store, and request queue collection clients.
• Updates the unit tests to pass enum members (StorageOwnership.OWNED_BY_ME / SHARED_WITH_ME) instead of raw strings.

Closes #700.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.61%. Comparing base (3d4ce3f) to head (4adeec7).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #735      +/-   ##
==========================================
+ Coverage   95.26%   95.61%   +0.35%     
==========================================
  Files          45       45              
  Lines        5115     5113       -2     
==========================================
+ Hits         4873     4889      +16     
+ Misses        242      224      -18     

Flag	Coverage Δ
integration	95.61% <100.00%> (+0.35%)	⬆️

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