fix(worker): N+1 query in ProcessFlakesTask

[sentry]

This PR addresses two N+1 query issues identified in app.tasks.flakes.ProcessFlakesTask, specifically within apps/worker/services/test_analytics/ta_process_flakes.py.

Problem:

1. Testrun Fetching: The process_flakes_for_commit function iterated over uploads, and for each upload, process_single_upload called get_testruns(upload), resulting in a separate database query for testruns per upload (N+1 queries).
2. Flake Expiration Saving: When a flake reached 30 recent passes in handle_pass, it would call .save() individually, leading to multiple single-row updates.

Solution:

1. Batch Testrun Fetching: Introduced get_testruns_for_uploads to fetch all relevant testruns for all uploads in a single batched query using upload_id__in=[...]. The process_single_upload function was refactored to accept pre-fetched testruns.
2. Bulk Flake Updates: Modified handle_pass to collect expired flakes into a list. After processing all uploads, these collected flakes are then updated in a single Flake.objects.bulk_update call.

These changes significantly reduce the database load and improve the performance of the ProcessFlakesTask by eliminating the N+1 query patterns.

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Fixes WORKER-YQ4

[codecov-notifications]

Codecov Report

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

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[sentry]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.90%. Comparing base (508927b) to head (89e4e3d).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1027   +/-   ##
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  Coverage   91.90%   91.90%           
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  Files        1318     1318           
  Lines       50711    50719    +8     
  Branches     1625     1625           
=======================================
+ Hits        46604    46612    +8     
  Misses       3801     3801           
  Partials      306      306           

Flag	Coverage Δ
workerintegration	58.54% <17.64%> (-0.03%)	⬇️
workerunit	90.35% <100.00%> (+<0.01%)	⬆️

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