Ensure -PtestGroups is passed through to unit tests

Issue: SPR-9984
Merge branch 'SPR-9984' into 3.2.x

* SPR-9984:
  Ensure -PtestGroups is passed through to unit tests
Attempt to repro ReflectionUtils performance issue

Issue: SPR-10197
Merge branch 'SPR-10197' into 3.2.x

* SPR-10197:
  Attempt to repro ReflectionUtils performance issue