feat(db-mongodb): support sorting by fields in other collections through a relationship field (#11803)

This is already supported in Postgres / SQLite.
For example:
```
const result = await payload.find({
  collection: 'directors',
  depth: 0,
  sort: '-movies.name', // movies is a relationship field here
})
```

Removes the condition in tests:
```
 // no support for sort by relation in mongodb
 if (isMongoose(payload)) {
  return
}
```