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 

That means his original commit https://github.com/bruno-infotrad/Elgg/commit/454deb638554533820afebf301c5fb9bc270358e was already ok??