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 when processing test analytics flakes.

Key changes include:

• Replaced the per-upload fetching of Testrun objects with a single batch query for all relevant uploads, significantly reducing the number of database calls.
• Batched individual flake.save() operations for expiring flakes into a single Flake.objects.bulk_update call, improving efficiency.
• Refactored the process_single_upload logic directly into process_flakes_for_commit to streamline the process.
• Ensured the uploads QuerySet is evaluated only once to prevent redundant database hits.

These changes aim to reduce database load and improve the overall performance of the flake processing task.

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Fixes WORKER-YYT

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.89%. Comparing base (701e991) to head (b17fc18).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1422   +/-   ##
=======================================
  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	58.53% <11.11%> (-0.03%)	⬇️
workerunit	90.37% <100.00%> (+<0.01%)	⬆️

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[codecov-notifications]

Codecov Report

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

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