[~aboldtch] identified that Micros-SystemGC needs to disable GC heuristics during its setup and this caused us to incorrectly identifying https://bugs.openjdk.org/browse/JDK-8350851 having a regression as the trick with modifying Xmn to avoid GC did not work for ZGC.

Ensuring that no GC will be triggered during setup with -XX:+ZCollectionIntervalOnly revealed that https://bugs.openjdk.org/browse/JDK-8347335 introduced a performance bug in this the Micros-SystemGC benchmark.