Draft: Rebalance CI partitions

What does this MR do and why?

Explores how to update partition_id id for the records affected in incident 8204.

Usage:

bin/bundle exec rake ci:partitioning:rebalance[100, 1, 200]

where 100 is the desired partition and (1, 200) represent the range of pipelines to be updated.

Related to #387301 (closed)

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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