Concurrency issue with order_insert

[beikov]

The ReactiveActionQueue was changed as part of 24b1d4b to use the singleton InsertActionSorter, which leads to a concurrency issue, because the class is not thread safe.
It looks like Reactive did not port/copy changes from the ORM change for HHH-16485, which fixes the problem as well handles other safety related aspects.

This was originally reported on the Quarkus issue tracker and was thought to be an ORM issue, but as I found out now, it is a problem of Hibernate Reactive only. For reference HHH-19900