Pipeline Graph Structural Update: Adding Accessors

What does this MR do?

This MR is the fourth of the MRs related to #276949 (closed).

It adds accessors for components that are not behind the flag but are consumed by both the GraphQL and REST components. This accounts fields that differ from one another in naming or position.

• app/assets/javascripts/pipelines/components/graph/job_item.vue
• app/assets/javascripts/jobs/mixins/delayed_job_mixin.js
• app/assets/javascripts/pipelines/components/graph/linked_pipeline.vue

The goal with the accessor is to have an obvious focus for removing unneeded accessors when the graph is completely replaced. The delayed_job_mixin does not use these accessors because, as it is used by multiple components, it will need to permanently access properties on both types.

This MR is successful to the extent does not change any layout or behavior.

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines
• Merge request performance guidelines
• Style guides

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Related to #276949 (closed)