Initialize the migration to convert pk to bigint for ci_pipelines

What does this MR do and why?

Prepare to convert pk to bigint for table ci_pipelines, see the first step https://docs.gitlab.com/ee/development/database/avoiding_downtime_in_migrations.html#migrating-integer-primary-keys-to-bigint

This is the performance of the migration in database lab.

Screenshots or screen recordings

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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

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #397000