fix: Batch testrun processing in ProcessFlakesTask

[sentry]

This PR addresses an N+1 query issue identified in the app.tasks.flakes.ProcessFlakesTask by refactoring the flake processing logic in apps/worker/services/test_analytics/ta_process_flakes.py.

Previously, the process_flakes_for_commit function iterated over each upload associated with a commit, calling process_single_upload for every one. This led to an N+1 query pattern where each process_single_upload call performed a separate SELECT and a separate bulk_update operation on the ta_timeseries_testrun table.

The fix consolidates these operations:

• The get_testruns function was updated to accept a list of upload IDs, allowing a single query to fetch all relevant testruns across multiple uploads.
• The process_single_upload function has been removed, and its logic integrated directly into process_flakes_for_commit.
• process_flakes_for_commit now fetches all testruns for all uploads in a single SELECT query, processes them in a single loop, and then performs a single Testrun.objects.bulk_update operation for all modified testruns.

This change significantly reduces the number of database calls, improving the performance of the ProcessFlakesTask.

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Fixes WORKER-YQ3

[sentry]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.90%. Comparing base (508927b) to head (160e942).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1025      +/-   ##
==========================================
- Coverage   91.90%   91.90%   -0.01%     
==========================================
  Files        1318     1318              
  Lines       50711    50706       -5     
  Branches     1625     1625              
==========================================
- Hits        46604    46599       -5     
  Misses       3801     3801              
  Partials      306      306              

Flag	Coverage Δ
workerintegration	58.57% <6.66%> (+<0.01%)	⬆️
workerunit	90.34% <100.00%> (-0.01%)	⬇️

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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