Draft: Remove N+1 query from register_job_service

What does this MR do?

This MR is related to this issue. This change removes the N+1 query problem for register_job_service. I want to mention that this MR is also related to #324369 (comment 534901267).

According to @allison.browne's analysis, ci_register_job_service_one_by_one was enabled on 11-March. After that, we see a huge volume of SQL calls. This MR tries to addresses the N+1 issue for ci_register_job_service_one_by_one.

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