fix(perf): Batch N+1 queries in ProcessFlakesTask

[sentry]

This PR addresses two N+1 query issues identified in the app.tasks.flakes.ProcessFlakesTask:

1. N+1 for Testrun fetching: Previously, process_flakes_for_commit iterated through each upload and called process_single_upload, which in turn called get_testruns(upload). This resulted in a separate database query for Testrun objects for each individual upload.

   • Fix: A new function, get_testruns_for_uploads, was introduced to fetch all relevant Testrun objects for all uploads in a single batched query. process_single_upload now receives a pre-filtered list of testruns, eliminating the N+1 query.

2. N+1 for expiring Flake saves: When a flake reached 30 recent passes in handle_pass, it would call flake.save() individually to update its end_date.

   • Fix: handle_pass now collects these expiring Flake objects into a list. process_flakes_for_commit then performs a single Flake.objects.bulk_update for all collected expiring flakes, significantly reducing database write operations.

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Fixes WORKER-YYV

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.89%. Comparing base (701e991) to head (a6f89ce).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1424   +/-   ##
=======================================
  Coverage   91.89%   91.89%           
=======================================
  Files        1325     1325           
  Lines       50868    50877    +9     
  Branches     1626     1626           
=======================================
+ Hits        46744    46753    +9     
  Misses       3818     3818           
  Partials      306      306           

Flag	Coverage Δ
workerintegration	58.53% <16.66%> (-0.03%)	⬇️
workerunit	90.38% <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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