The Title

Add "Show child pages" button in the page listing dropdown

The description

Fixes #11974

Summary

This PR adds a "Show child pages" button to the dropdown menu in PageListingViewSet, which allows the users to navigate directly to the child pages from the listing view, removing the need to click through the "Edit" page to find the breadcrumbs.

Changes

• Added PageListingShowChildPagesButton to wagtail/admin/wagtail_hooks.py
• The button only appears when the page has child pages (i.e numChild>0)
• Added unit tests to wagtail/admin/tests/pages/test_explorer_view.py for verification

Screenshot

Testing

• Verified button appears only for parent page
• Verified link navigates to the explorer view
• All admin tests passed.

AI Assistance Disclaimer
This pull request includes unit test written with the assistance of AI. This code was reviewed, tested, and verified by me. I understand the implementation and take full accountability for it.