fix(worker): Optimize N+1 query in ProcessFlakesTask

[sentry]

This PR addresses an N+1 query performance issue identified in app.tasks.flakes.ProcessFlakesTask, specifically within the services.test_analytics.ta_process_flakes.py module.

Problem:
Previously, the process_flakes_for_commit function would iterate over each ReportSession (upload) and, for every upload, execute a separate database query to fetch its associated Testrun objects via get_testruns(upload). This led to an N+1 query pattern, where 1 query fetched the uploads, and then N additional queries were made for the testruns, significantly impacting performance for commits with many uploads.

Solution:
To resolve this, the Testrun objects for all relevant uploads are now fetched in a single batch query using upload_id__in before the iteration begins. A new helper function, get_testruns_for_uploads, handles this batch fetching and groups the results by upload_id in Python. The process_single_upload function was updated to accept these pre-fetched and grouped testruns, eliminating the need for individual database calls within the loop.

Impact:
This change reduces the number of database queries from an N+1 pattern (1 for uploads + N for testruns) to a constant 2 queries (1 for uploads + 1 for all testruns), regardless of the number of uploads, thereby improving the efficiency and performance of the ProcessFlakesTask.

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Fixes WORKER-YYH

[codecov]

Codecov Report

❌ Patch coverage is 92.30769% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 91.88%. Comparing base (701e991) to head (cedb2f7).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...orker/services/test_analytics/ta_process_flakes.py	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1410      +/-   ##
==========================================
- Coverage   91.89%   91.88%   -0.01%     
==========================================
  Files        1325     1325              
  Lines       50868    50878      +10     
  Branches     1626     1626              
==========================================
+ Hits        46744    46751       +7     
- Misses       3818     3821       +3     
  Partials      306      306              

Flag	Coverage Δ
workerintegration	58.54% <15.38%> (-0.03%)	⬇️
workerunit	90.36% <92.30%> (-0.02%)	⬇️

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[codecov-notifications]

Codecov Report

❌ Patch coverage is 92.30769% with 1 line in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...orker/services/test_analytics/ta_process_flakes.py	92.30%	1 Missing ⚠️

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