[SL-148] Layout listing updates

[rafsuntaskin]

🎫 Ticket

SL-148

🗒️ Description

• Layout Edit link opens up iframe view to edit the layout.
• Changed the layout card text “No upcoming events” to “No associated events” when a layout has no associated events of any kind.
• Count and display the number of associated events when available and hide the delete button.

🎥 Artifacts

📷 screenshot(s): https://share.cleanshot.com/10qqbFBK

✔️ Checklist

• Changelog entry in the readme.txt file.
• Code is covered by NEW wpunit or integration tests.
• Code is covered by EXISTING wpunit or integration tests.
• Are all the required tests passing?
• Automated code review comments are addressed.
• Have you added Artifacts?
• Check the base branch for your PR.
• Add your PR to the project board for the release.