fix(worker): Eliminate N+1 queries in ProcessFlakesTask

[sentry]

This PR addresses an N+1 query performance issue within the app.tasks.flakes.ProcessFlakesTask by optimizing database interactions in apps/worker/services/test_analytics/ta_process_flakes.py.

Problem:

1. The process_flakes_for_commit function iterated over uploads, and for each upload, process_single_upload would execute a separate database query (get_testruns) to fetch associated testruns. This led to N+1 queries where N is the number of uploads.
2. When a flake's recent_passes_count reached 30 in handle_pass, an individual flake.save() call was made, leading to another N+1 pattern for expiring flakes.

Solution:

1. Bulk-fetching Testruns: Introduced get_testruns_for_uploads to fetch all relevant testruns for all uploads in a single database query. These testruns are then pre-grouped by upload_id and passed to process_single_upload, eliminating the per-upload query.
2. Batch-updating Expiring Flakes: Modified handle_pass to no longer call flake.save() directly. Instead, expiring flakes are collected into a list (expired_flakes) and then updated in a single Flake.objects.bulk_update call at the end of process_flakes_for_commit.

These changes significantly reduce the number of database round-trips, improving the performance of the ProcessFlakesTask.

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Fixes WORKER-YYZ

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.89%. Comparing base (701e991) to head (36e0ac0).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1428   +/-   ##
=======================================
  Coverage   91.89%   91.89%           
=======================================
  Files        1325     1325           
  Lines       50868    50874    +6     
  Branches     1626     1626           
=======================================
+ Hits        46744    46750    +6     
  Misses       3818     3818           
  Partials      306      306           

Flag	Coverage Δ
workerintegration	58.54% <17.64%> (-0.03%)	⬇️
workerunit	90.37% <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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