foreachParN_ should not use more than 'n' fibers #4346
                
     Merged
            
            
          
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In #1187,
foreachParNwas fixed to avoid creating 'n' fibers all sharing a semaphore, butforeachParN_was left with the old behavior, leading to dramatic performance with large collections.I reused the implementation of
foreachParNbut simplified it since we don't need to collect results.