SPM-3701 added four spilling metrics in all stages that spill

• spills // The number of times the stage has spilled
• spilledBytes // The amount in bytes of main memory that has been spilled
• spilledRecords // The number of records that have been spilled
• spilledDataStorageSize // The amount in bytes that spilling has taken up on disk

In explain output, some stages include metrics with similar meaning as the above but different names:

• in HashLookupStage and HashLookupUnwindStage, spilledBytesApprox has the same purpose as spilledBytes
• in DocumentSourceGroupbase and DocumentSourceSetInternalSetWindowFields, numBytesSpilledEstimate has the same purpose as spilledBytes

SPM-3701 added the new metrics in the explain output but did not remove the existing ones. If customers do not use those explain outputs, it will be nice to remove them and keep only the newly added metrics that are consistent across all stages.