8025441: G1: assert "assert(thread < _num_vtimes) failed: just checking" fails when G1ConcRefinementThreads > ParallelGCThreads
Summary: The initialization for the remembered set summary data structures used the wrong thread count, i.e. number of worker threads instead of number of refinement threads.
Reviewed-by: brutisso

Summary: Fixed the output of G1SummarizeRSetStats: too small datatype for the number of concurrently processed cards, added concurrent remembered set thread time retrieval for Linux and Windows (BSD uses os::elapsedTime() now), and other cleanup. The information presented during VM operation is now relative to the previous output, not always cumulative if G1SummarizeRSetStatsPeriod > 0. At VM exit, the code prints a cumulative summary.
Reviewed-by: johnc, jwilhelm