Separate EE issue board e2e spec components

What does this MR do?

Building off of a previous MR, this separates EE specific methods for issue board components in e2e specs.

Uses the new PageConcern module

Fixes #218232 (closed)

Screenshots

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