Resolve "Track failed batched jobs metric"

What does this MR do and why?

We had to deprecate the old metric because of a query not supported by the Snowflake platform. More info here: https://gitlab.com/gitlab-data/analytics/-/issues/18216

In this merge request, we add the batched_background_migration_count_failed_jobs_metric back with the query fixed. This time, we are only doing one count.

Query:

SELECT "batched_background_migrations"."table_name", "batched_background_migrations"."job_class_name", COUNT(batched_jobs) AS number_of_failed_jobs
FROM "batched_background_migrations"
INNER JOIN "batched_background_migration_jobs" "batched_jobs" ON "batched_jobs"."batched_background_migration_id" = "batched_background_migrations"."id"
WHERE "batched_jobs"."status" = 2
GROUP BY "batched_background_migrations"."table_name", "batched_background_migrations"."job_class_name"

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Related to #416718 (closed)