Move issues routes under /-/ scope

What does this MR do?

Moves all issues routes under /-/ scope. For #118849 (closed)

This will make issues routes to use - scope by default but old routes are still served. As result there is no need to change every occurrence of issues path to - one. We will do it in 13.0 when we deprecate old route and add redirect from /issues to /-/issues per #118849 (closed)

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.