[DOP-22578] Return statistics in GET /locations

[dolfinus]

Change Summary

Changed the response schema of GET /locations and PATCH /locations/:id to include dataset & job statistics. This is useful to show in list of locations, or to show/hide tabs with datasets/jobs list on LocationShow page.

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 98.75000% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.14%. Comparing base (e2f8346) to head (e1d22ca).
Report is 136 commits behind head on develop.

Files with missing lines	Patch %	Lines
data_rentgen/server/services/location.py	97.87%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #160      +/-   ##
===========================================
+ Coverage    93.04%   93.14%   +0.09%     
===========================================
  Files          182      183       +1     
  Lines         4115     4188      +73     
  Branches       277      281       +4     
===========================================
+ Hits          3829     3901      +72     
- Misses         224      225       +1     
  Partials        62       62              

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