chore: Improve insertReportIntoSizes to reduce memory allocations (#7456)

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**What changed?**
Improve insertReportIntoSizes to reduce memory allocations

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**Why?**
To reduce memory allocation

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unit tests (this method is covered by unit test)

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**Documentation Changes**

Author: Shaddoll

service/worker/scanner/shardscanner/aggregators.go

@@ -497,10 +497,9 @@ func (a *ShardScanResultAggregator) insertReportIntoSizes(report ScanReport) {
 		}
 		insertIndex++
 	}
-	newShardSizes := append([]ShardSizeTuple{}, a.shardSizes[0:insertIndex]...)
-	newShardSizes = append(newShardSizes, tuple)
-	newShardSizes = append(newShardSizes, a.shardSizes[insertIndex:]...)
-	a.shardSizes = newShardSizes
+	a.shardSizes = append(a.shardSizes, ShardSizeTuple{})
+	copy(a.shardSizes[insertIndex+1:], a.shardSizes[insertIndex:])
+	a.shardSizes[insertIndex] = tuple
 }
 
 // GetShardDistributionStats returns aggregated size statistics