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 request #7012 
You must verify $container because a group can be hidden while the page it's in is not. In that case without checking the user would get a fatal error.