[DOP-22578] Return statistics in GET /operations

[dolfinus]

Change Summary

Changed the response schema of GET /operations to include inputs & outputs statistics. This is useful to show in list of operations within run.
Don't change response for lineage, as it includes inputs & outputs are distinct relations.

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[codecov]

Codecov Report

Attention: Patch coverage is 98.68421% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.92%. Comparing base (7fa0d2d) to head (9a79331).
Report is 138 commits behind head on develop.

Files with missing lines	Patch %	Lines
data_rentgen/server/services/operation.py	97.43%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #158      +/-   ##
===========================================
+ Coverage    92.82%   92.92%   +0.10%     
===========================================
  Files          180      181       +1     
  Lines         3956     4027      +71     
  Branches       269      272       +3     
===========================================
+ Hits          3672     3742      +70     
- Misses         222      223       +1     
  Partials        62       62              

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