There is a circular dependency between between PSParallelCompact and ParCompactionManager that makes it hard to move ParCompactionManager::push to psCompactionManager.inline.hpp, something that we need for JDK-8076177.

The circular dependency can be seen with:
 <the follow contents functions in psCompactionManager.cpp>
  PSParallelCompact::mark_and_push
   ParCompactionManager::push

The suggested fix is to make mark_and_push a member of ParCompactionManager. The implementation already takes a ParCompactionManager as the first argument and it's used by other ParCompactionManager specific functions.

The fix also moves the rest of the follow_* functions so that all marking code, which is done in multiple threads using separate ParCompactionManagers, are held together.