fix(ta): batch testrun updates in ProcessFlakesTask

[sentry]

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

Problem:
Previously, the process_flakes_for_commit function iterated over each upload, calling process_single_upload for every item. Each call to process_single_upload then executed a separate SELECT query via get_testruns and a bulk_update on the ta_timeseries_testrun table. This resulted in an N+1 query pattern, where N is the number of uploads, leading to inefficient database operations.

Solution:
To resolve this, the following changes were implemented:

1. get_testruns function modified: It now accepts a list of upload_ids and filters Testrun objects using upload_id__in, allowing all relevant testruns to be fetched in a single database query.
2. process_single_upload replaced by process_all_uploads: The logic for processing testruns (handling passes and failures) was consolidated into a new function, process_all_uploads. This function operates on all testruns fetched in bulk and performs a single Testrun.objects.bulk_update at the end.
3. process_flakes_for_commit updated: The loop iterating over individual uploads and calling process_single_upload has been removed. Instead, process_flakes_for_commit now collects all upload IDs and passes them to the new process_all_uploads function, effectively reducing N SELECTs + N UPDATEs to a single SELECT + a single UPDATE operation.

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Fixes WORKER-YNC