[5.6] Fix MorphTo lazy loading and withoutGlobalScopes()

[staudenmeir]

#25331 fixed withoutGlobalScopes() when eager loading MorphTo relationships.
This broke lazy loading:

class Comment extends Model
{
    public function commentable()
    {
        return $this->morphTo()->withoutGlobalScopes();
    }
}

class Post extends Model
{
    use SoftDeletes;
}

Comment::first()->commentable;

# expected
select * from "posts" where "posts"."id" = ? limit 1

# actual
select * from "posts" where "posts"."id" = ? and "posts"."deleted_at" is null limit 1

The $macroBuffer is only used for eager loading. For lazy loading, we have to pass withoutGlobalScopes() through to the query.

Fixes #25402.