Draft: POC Deduplicate intrinsic immutable data to Ci::JobInfo

What does this MR do and why?

This is a POC for moving immutable, intrinsic data into a new model Ci::JobInfo. Details:

1. The Ci::JobInfo model mirrors Ci::JobDefinition. The difference is that there is no separate association table (like ci_job_definition_instances). Instead, ci_builds has a direct belongs_to relationship to ci_job_infos.

2. Attempts to move the following columns from ci_builds into ci_job_infos:

• allow_failure --> Cannot move. This field is mutated when job transitions to failed.
• when --> Cannot move. This field is mutated in Ci::ProcessBuildService.
• scheduling_type
• stage_idx --> Same as name.
• name --> Indexed column; impractical to move. Decided to keep it in ci_builds for now but still copy data over to ci_job_infos to drop ci_build_names. See !211540 (comment 2878147699).

3. Attempts to move ci_build_names data into ci_job_infos.name column, which is set up with a search_vector column.

References

• Spike: Deduplicate intrinsic immutable data fro... (#577211 - closed)
• Spike: Deduplicate `ci_build_names` into one of... (#567704 - closed)

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #577211 (closed)