fix(perf): Eliminate N+1 query in ProcessFlakesTask

[sentry]

This PR addresses an N+1 query performance issue identified in app.tasks.flakes.ProcessFlakesTask.

Problem:
Previously, the process_flakes_for_commit function would iterate over each upload associated with a commit and, for every upload, execute a separate database query to fetch its related testruns. This resulted in an N+1 query pattern, where N is the number of uploads, leading to inefficient database usage.

Additionally, the handle_pass function would perform individual .save() operations on Flake objects when they reached a certain pass count, contributing to more single-row database operations.

Solution:

1. Batched Testrun Fetching: The get_testruns function has been replaced with get_testruns_for_uploads. This new function fetches all relevant testruns for all uploads associated with a commit in a single batched query, significantly reducing the number of database calls from N to 1.
2. Batched Flake Updates: The handle_pass function no longer performs individual .save() calls. Instead, expired Flake objects are collected into a list and then included in the existing Flake.objects.bulk_create operation at the end of process_flakes_for_commit. This eliminates individual update queries for expired flakes.

These changes drastically reduce the database load and improve the performance of the ProcessFlakesTask by converting multiple individual queries into highly optimized bulk operations.

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Fixes WORKER-YYQ

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.89%. Comparing base (701e991) to head (8ea071c).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1416   +/-   ##
=======================================
  Coverage   91.89%   91.89%           
=======================================
  Files        1325     1325           
  Lines       50868    50873    +5     
  Branches     1626     1626           
=======================================
+ Hits        46744    46749    +5     
  Misses       3818     3818           
  Partials      306      306           

Flag	Coverage Δ
workerintegration	58.54% <14.28%> (-0.02%)	⬇️
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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