Add stack depth check to QueueFKConstraintValidation().

Add stack depth check to QueueFKConstraintValidation().

QueueFKConstraintValidation() recurses through the partition hierarchy
to queue child constraint validations and to mark child rows as
validated.  With a sufficiently deep partition tree, this can result
in a stack-overflow crash.  Defend against that as we do elsewhere.

Bug: #19482
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Author: Ayush Tiwari <ayushtiwari.slg01@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/19482-4cc37cbf52d55235@postgresql.org
Backpatch-through: 18