PHPORM-238 Add support for `withCount` and other aggregations

[GromNaN]

Fix PHPORM-238

Implement this feature from Laravel: https://laravel.com/docs/11.x/eloquent-relationships#counting-related-models Counting relations with SQL is done using a subquery. For MongoDB, there is 2 ways:

1. Making a query during eager loading, that count the objects for each result ID. This is an aggregation with a $group by foreign key.
2. Using $lookup to load references and count them. The process would be similar for embedded relations (without the $lookup). But this doesn't work with hybrid relations.

Checklist

• [x] Add tests and ensure they pass
• [x] Support mongodb relationships
• [x] CANCELLED: Support hybrid relationships (PR reverted from Laravel: https://github.com/laravel/framework/pull/53679)
• [x] Support embedded relationships, contraint query not supported PHPORM-292