Fix partition_id for p_ci_builds_metadata

Ref: #387301 (closed)

What does this MR do and why?

This MR fixes invalid p_ci_builds_metadata records in production and sets the partition_id to 100.

Database

We have around ~3.5M records to fix.

Following a similar strategy used in !111287 (merged), I choose a default batch size of 5_000 and a sub batch size of 500.

select count(*) from p_ci_builds_metadata where partition_id = 101;

📝 This seems to be the query executed by our background migration and its associated query plan.

UPDATE p_ci_builds_metadata
SET partition_id = 100
WHERE p_ci_builds_metadata.id BETWEEN 100000 AND 100500
AND p_ci_builds_metadata.partition_id = 101

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