CloudWatch: Add Missing Elasticache Host-level metrics (#43455)

Add missing host-level Elasticache metrics from https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/CacheMetrics.HostLevel.html

Follows from https://github.com/grafana/grafana/pull/43336#issuecomment-999367311

pkg/tsdb/cloudwatch/metrics.go

@@ -235,6 +235,8 @@ var metricsMap = map[string][]string{
 		"BytesWrittenToDisk",
 		"BytesWrittenOutFromMemcached",
 		"CPUUtilization",
+		"CPUCreditBalance",
+		"CPUCreditUsage",
 		"CacheHitRate",
 		"CacheHits",
 		"CacheMisses",
@@ -289,6 +291,13 @@ var metricsMap = map[string][]string{
 		"MemoryFragmentationRatio",
 		"NetworkBytesIn",
 		"NetworkBytesOut",
+		"NetworkPacketsIn",
+		"NetworkPacketsOut",
+		"NetworkBandwidthInAllowanceExceeded",
+		"NetworkBandwidthOutAllowanceExceeded",
+		"NetworkConntrackAllowanceExceeded",
+		"NetworkLinkLocalAllowanceExceeded",
+		"NetworkPacketsPerSecondAllowanceExceeded",
 		"NewConnections",
 		"NewItems",
 		"NumItemsReadFromDisk",