Possible performance improvement

I've had a go at a patch for this and confirmed no difference in the $children array for my test case.

Limitation of my patch is that it assumes all children will be the same entity type as the one being validated, which based on the field definitions, I believe is a safe assumption. Could alter the query to include the type otherwise.

This patch means we don't run out of memory with 28k children nodes (don't ask).
On a page with 6 children... the entity query appears marginally slower. 4.1 seconds (entity query) vs 3.55 seconds (loadMultiple).

Improving patch with early exit for no descendants and adding accessCheck() for query.

Small logic fix. Tests don't cover the case where there is a recursive reference to self.

I think this is ready for a review.

Thanks, committed. This will go out as 3.3.6 which I'll tag shortly

Automatically closed - issue fixed for 2 weeks with no activity.