fix(test_analytics): Eliminate N+1 queries in flake processing

[sentry]

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

Problem:

1. Previously, process_flakes_for_commit would iterate over each upload and call get_testruns(upload), resulting in a separate database query for Testrun objects for every single upload. This led to an N+1 query pattern where N is the number of uploads.
2. Additionally, handle_pass would call .save() individually for each Flake object that reached 30 recent passes, leading to multiple single-row updates.

Solution:

1. Introduced get_testruns_for_uploads to fetch all relevant Testrun objects for all uploads in a single batched query using upload_id__in. These testruns are then grouped by upload_id and passed to process_single_upload.
2. Modified handle_pass to collect expired Flake objects into a list. After processing all uploads, these collected flakes are updated in a single Flake.objects.bulk_update call.

Impact:
This change significantly reduces the number of database queries executed during flake processing, improving the performance and efficiency of the ProcessFlakesTask.

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Fixes WORKER-YTE