Display commit title when no pipeline name - UX adjustment

What does this MR do and why?

UX adjustment for pipeline details header refactor. Display the commit title when there is no pipeline name defined.

First MR: !120634 (merged)

Second MR: !121174 (merged)

Third MR: !122216 (merged)

Fourth MR: !122516 (merged)

Design can be found here #394768[Unbox-pipeline-detail-page.png]

Screenshots or screen recordings

How to set up and validate locally

1. Enable pipeline_details_header_vue in the rails console
2. Visit a pipeline (with no defined pipeline name)
3. View the header section

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #394768 (closed)