[DOP-22578] Change response schema of GET /datasets

[dolfinus]

Change Summary

Changed the response schema of GET /datasets to match other endpoints (#158, #159, #160, #162). For now there is no statistics for dataset, but it can be added later (e.g. inputs/outputs stats within last day/week/month) without breaking backward compatibility.

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 95.83333% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.15%. Comparing base (5e52684) to head (b521950).
Report is 135 commits behind head on develop.

Files with missing lines	Patch %	Lines
data_rentgen/server/services/dataset.py	94.11%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #161   +/-   ##
========================================
  Coverage    93.14%   93.15%           
========================================
  Files          183      184    +1     
  Lines         4188     4208   +20     
  Branches       281      281           
========================================
+ Hits          3901     3920   +19     
- Misses         225      226    +1     
  Partials        62       62           

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