* Refactor ForEachProcessor to use iteration instead of recursion
This change makes ForEachProcessor iterative and still non-blocking.
In case of non-async processors we use single for loop and no recursion at all.
In case of async processors we continue work on either current thread or thread
started by downstream processor, whichever is slower (usually processor thread).
Everything is synchronised by single atomic variable.
Relates #50514
a4da1c9b46