SERVER-92994 implemented accumulator level spilling where the PercentileAlgo object owns the spill file, so it's created and destroyed each time the accumulator is reset. This ticket will modify this so that the accumulator owns the spill file and will reset it (truncate or wipe without destroying) when the accumulator is reset so that it's only created and destroyed once.

*Note: The described improvement is now included as a part of SERVER-92994, so a separate pull request isn't needed.