Use virtual threads to model test users #624
Description
In XLT, test users are represented by separate threads that repeatedly execute a test case. While this concept is programmer-friendly, it does not scale well when heavyweight platform threads are used. Ten or twenty thousand platform threads could overload a test machine.
Load tests where up to a hundred thousand parallel test activities should be simulated on a single machine are not possible this way. However, since XLT is now based on Java 21, we can use virtual threads instead, which are much more lightweight.