fix(test_analytics): Resolve N+1 query in ProcessFlakesTask

[sentry]

This PR addresses an N+1 query performance issue within the app.tasks.flakes.ProcessFlakesTask.

Problem:
Previously, the process_flakes_for_commit function would fetch all uploads for a given commit. Then, for each individual upload, it would call process_single_upload, which in turn executed a separate database query to retrieve Testrun objects associated with that specific upload. This led to an N+1 query pattern, where N is the number of uploads for a commit, causing significant database overhead and slower task execution.

Solution:

1. Batch Fetching of Testruns: The get_testruns function was refactored into get_testruns_for_uploads. This new function now accepts a list of upload_ids and fetches all relevant Testrun objects for all these uploads in a single batched query. The results are then grouped by upload_id for efficient access.
2. Updated process_single_upload: The process_single_upload function was updated to accept the pre-fetched list of Testrun objects directly, eliminating its internal database query.
3. Consolidated bulk_update: Instead of performing Testrun.objects.bulk_update for each upload within the loop, all modified Testrun objects are now collected, and a single bulk_update operation is performed after processing all uploads for the commit.

Impact:
This change significantly reduces the number of database queries from 1 + N (where N is the number of uploads) to a fixed 2 queries (one for uploads, one for all associated testruns), drastically improving the performance and reducing the database load for ProcessFlakesTask executions, especially for commits with a large number of test result uploads.

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Fixes WORKER-YTZ

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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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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.89%. Comparing base (e682d07) to head (634d534).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1229   +/-   ##
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  Coverage   91.89%   91.89%           
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  Files        1325     1325           
  Lines       50868    50875    +7     
  Branches     1626     1626           
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+ Hits        46744    46751    +7     
  Misses       3818     3818           
  Partials      306      306           

Flag	Coverage Δ
workerintegration	58.54% <7.14%> (-0.03%)	⬇️
workerunit	90.38% <100.00%> (+<0.01%)	⬆️

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