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 

it should probably be 
```
if (!$container) {
   return false;
}
```
as otherwise the function could return void (which is not expected)

Also look at how to squash commits as core would like to keep the commit history clean (google squashing commits to see how to do that)