Pipeline Graph Structural Update: Add Link Perf

What does this MR do?

This adds the performance calls for the link calculation, an important metric to check whether the new graph is behaving well. As usual, this is behind the graphql_pipeline_details feature flag, which is currently off for all users except individuals in the beta. The backend is behind its own flag (see !52820 (merged)).

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Related to #276949 (closed)