Resolve "Change single-item breadcrumbs to page titles"

What does this MR do?

Changes single-item breadcrumbs to page titles

TODO

• Projects
• Groups
• Activity
• Snippets
• Issues
• Merge Requests
• Milestones
• Welcome to GitLab (No projects)
• Todos

Screenshots

What are the relevant issue numbers?

#51955 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides

Closes #51955 (closed)