Change block_arrival_latency buckets to exponential format (#8065)

Co-authored-by: Preston Van Loon <preston@prysmaticlabs.com>
Co-authored-by: Raul Jordan <raul@prysmaticlabs.com>
Co-authored-by: terence tsao <terence@prysmaticlabs.com>

beacon-chain/sync/metrics.go

@@ -51,7 +51,7 @@ var (
 		prometheus.HistogramOpts{
 			Name:    "block_arrival_latency_milliseconds",
 			Help:    "Captures blocks propagation time. Blocks arrival in milliseconds distribution",
-			Buckets: []float64{1000, 2000, 3000, 4000, 5000, 6000},
+			Buckets: []float64{250, 500, 1000, 1500, 2000, 4000, 8000, 16000},
 		},
 	)
 )