Add multiple entry points to merge train detail page

Release notes

Problem to solve

We are nearing the completion of the development of #277391 (closed) and the design only has a single entry point that appears in the pipeline status widget once a train has started. This can be easy to miss if user isn't tracking the merge train pipeline from the merge request page.

Intended users

Sasha

User experience goal

The merge train detail page entry point should be available at strategic location for easy access.

Proposal

1, Add hyperlink to all the system messages in MR that mentions merge trains #469149 (comment 1994023319)

2. Move bulk edit to dropdown on MR list view, and add a link variant button for View merge train details in that space: #469149 (comment 2010911018)
3. Add link to enter merge train page from the pipeline detail page of a merge train pipeline: proposal

Further details

Permissions and Security

Documentation

Availability & Testing

Available Tier

Feature Usage Metrics

What does success look like, and how can we measure that?

What is the type of buyer?

Is this a cross-stage feature?

What is the competitive advantage or differentiation for this feature?

Links / references