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

[sentry]

This PR addresses an N+1 query issue identified in the app.tasks.flakes.ProcessFlakesTask, specifically within the services.test_analytics.ta_process_flakes.py module.

Problem:

1. Testrun Fetching: The process_flakes_for_commit function iterated over ReportSession objects (uploads), and for each upload, it called process_single_upload. Inside process_single_upload, get_testruns(upload) was called, resulting in a separate database query for testruns for each upload. This led to N+1 queries where N is the number of uploads for a given commit.
2. Flake Expiration Saves: When a flake met its expiration criteria in handle_pass, it would immediately call .save() on the individual Flake object, leading to multiple individual update queries if many flakes expired in a single run.

Solution:

1. Batch Testrun Fetching: A new helper function, get_testruns_for_uploads, was introduced. This function now fetches all relevant testruns for all uploads associated with a commit in a single batched query using upload_id__in. The results are then grouped by upload_id and passed to process_single_upload.
2. Batch Flake Updates: The handle_pass function no longer calls .save() directly. Instead, expiring Flake objects are collected into a list (expired_flakes). After all uploads and testruns have been processed, a single Flake.objects.bulk_update is performed on all collected expired_flakes.

These changes significantly reduce the number of database queries, improving the performance and efficiency of the ProcessFlakesTask.

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Fixes WORKER-YV7

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.89%. Comparing base (e682d07) to head (b1814fe).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1237   +/-   ##
=======================================
  Coverage   91.89%   91.89%           
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  Files        1325     1325           
  Lines       50868    50874    +6     
  Branches     1626     1626           
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+ Hits        46744    46750    +6     
  Misses       3818     3818           
  Partials      306      306           

Flag	Coverage Δ
workerintegration	58.54% <13.33%> (-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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