Audit concurrency in OLAP mode

[systay]

We have recently found two different issues coming from TryStreamExecute on engine primitives not being concurrently safe.

We have to go over all the engine primitives and make sure that they are properly protected against bad concurrent use. One good way of doing this is to make sure to write unit test for all engine primitives and then run these with race detection enabled.

#14435 fixes one of these issues, and we recently found the same kind of problem on the memory_sort.go