fix(pages): add canEdit to page deletion permission check


Description: using canEdit allows plugins to override the delete permission check (e.g. groups owners in the group_tools plugin). I did not mark the function pages_can_delete_page in lib/pages as private since it could be used by other plugins.

Fixes #7007

Duplicate of pull requests #7012 and #7645 

FYI the ternary operates just like an if/else. It already does the container check in a safe way: If $container is falsey, canEdit() is not executed and false is returned. No need for the surrounding if block.