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 
Can be boiled down to:

```php
$container = $page->getContainerEntity();
return $container ? $container->canEdit() : false;
```