Prepare partitioning constraint for ci_job_artifacts

Ref: #428986 (closed)

What does this MR do and why?

This MR enqueues a job which will create a new constraint this weekend on ci_job_artifacts for gitlab.com.

This is a similar approach we used for ci_pipeline_variables in !137643 (merged).

Why are we doing this?

This is a prerequisite in order to partition this table.

https://docs.gitlab.com/ee/development/database/partitioning/list.html#step-6---create-parent-table-and-attach-existing-table-as-the-initial-partition