Cloudwatch: Add support for AWS/PrivateLink* metrics and dimensions (#45515)

Add support for AWS/PrivateLink{Endpoints,Interfaces} metrics and
dimensions. Change is based on the official AWS documentation[1].

1. https://docs.aws.amazon.com/vpc/latest/privatelink/privatelink-cloudwatch-metrics.html

pkg/tsdb/cloudwatch/metrics.go

@@ -362,6 +362,8 @@ var metricsMap = map[string][]string{
 	"AWS/NetworkFirewall":      {"DroppedPackets", "Packets", "PassedPackets", "ReceivedPacketCount"},
 	"AWS/OpsWorks":             {"cpu_idle", "cpu_nice", "cpu_steal", "cpu_system", "cpu_user", "cpu_waitio", "load_1", "load_15", "load_5", "memory_buffers", "memory_cached", "memory_free", "memory_swap", "memory_total", "memory_used", "procs"},
 	"AWS/Polly":                {"2XXCount", "4XXCount", "5XXCount", "RequestCharacters", "ResponseLatency"},
+	"AWS/PrivateLinkEndpoints": {"ActiveConnections", "BytesProcessed", "NewConnections", "PacketsDropped", "RstPacketsReceived"},
+	"AWS/PrivateLinkServices":  {"ActiveConnections", "BytesProcessed", "EndpointsCount", "NewConnections", "RstPacketsReceived"},
 	"AWS/RDS":                  {"ActiveTransactions", "AuroraBinlogReplicaLag", "AuroraGlobalDBDataTransferBytes", "AuroraGlobalDBReplicatedWriteIO", "AuroraGlobalDBReplicationLag", "AuroraReplicaLag", "AuroraReplicaLagMaximum", "AuroraReplicaLagMinimum", "AvailabilityPercentage", "BacktrackChangeRecordsCreationRate", "BacktrackChangeRecordsStored", "BacktrackWindowActual", "BacktrackWindowAlert", "BackupRetentionPeriodStorageUsed", "BinLogDiskUsage", "BlockedTransactions", "BufferCacheHitRatio", "BurstBalance", "CPUCreditBalance", "CPUCreditUsage", "CPUUtilization", "ClientConnections", "ClientConnectionsClosed", "ClientConnectionsNoTLS", "ClientConnectionsReceived", "ClientConnectionsSetupFailedAuth", "ClientConnectionsSetupSucceeded", "ClientConnectionsTLS", "CommitLatency", "CommitThroughput", "DDLLatency", "DDLThroughput", "DMLLatency", "DMLThroughput", "DatabaseConnectionRequests", "DatabaseConnectionRequestsWithTLS", "DatabaseConnections", "DatabaseConnectionsBorrowLatency", "DatabaseConnectionsCurrentlyBorrowed", "DatabaseConnectionsCurrentlyInTransaction", "DatabaseConnectionsCurrentlySessionPinned", "DatabaseConnectionsSetupFailed", "DatabaseConnectionsSetupSucceeded", "DatabaseConnectionsWithTLS", "Deadlocks", "DeleteLatency", "DeleteThroughput", "DiskQueueDepth", "EngineUptime", "FailedSQLServerAgentJobsCount", "FreeLocalStorage", "FreeStorageSpace", "FreeableMemory", "InsertLatency", "InsertThroughput", "LoginFailures", "MaxDatabaseConnectionsAllowed", "MaximumUsedTransactionIDs", "NetworkReceiveThroughput", "NetworkThroughput", "NetworkTransmitThroughput", "OldestReplicationSlotLag", "Queries", "QueryDatabaseResponseLatency", "QueryRequests", "QueryRequestsNoTLS", "QueryRequestsTLS", "QueryResponseLatency", "RDSToAuroraPostgreSQLReplicaLag", "ReadIOPS", "ReadLatency", "ReadThroughput", "ReplicaLag", "ReplicationSlotDiskUsage", "ResultSetCacheHitRatio", "SelectLatency", "SelectThroughput", "ServerlessDatabaseCapacity", "SnapshotStorageUsed", "SwapUsage", "TotalBackupStorageBilled", "TransactionLogsDiskUsage", "TransactionLogsGeneration", "UpdateLatency", "UpdateThroughput", "VolumeBytesUsed", "VolumeReadIOPs", "VolumeWriteIOPs", "WriteIOPS", "WriteLatency", "WriteThroughput"},
 	"AWS/Redshift":             {"CommitQueueLength", "ConcurrencyScalingActiveClusters", "ConcurrencyScalingSeconds", "CPUUtilization", "DatabaseConnections", "HealthStatus", "MaintenanceMode", "MaxConfiguredConcurrencyScalingClusters", "NetworkReceiveThroughput", "NetworkTransmitThroughput", "PercentageDiskSpaceUsed", "QueriesCompletedPerSecond", "QueryDuration", "QueryRuntimeBreakdown", "ReadIOPS", "ReadLatency", "ReadThroughput", "TotalTableCount", "WLMQueueLength", "WLMQueueWaitTime", "WLMQueriesCompletedPerSecond", "WLMQueryDuration", "WLMRunningQueries", "WriteIOPS", "WriteLatency", "WriteThroughput", "SchemaQuota", "NumExceededSchemaQuotas", "StorageUsed", "PercentageQuotaUsed"},
 	"AWS/Robomaker":            {"RealTimeFactor", "vCPU", "Memory", "SimulationUnit"},
@@ -473,6 +475,8 @@ var dimensionsMap = map[string][]string{
 	"AWS/NetworkFirewall":         {"AvailabilityZone", "CustomAction", "Engine", "FirewallName"},
 	"AWS/OpsWorks":                {"InstanceId", "LayerId", "StackId"},
 	"AWS/Polly":                   {"Operation"},
+	"AWS/PrivateLinkEndpoints":    {"Endpoint Type", "Service Name", "Subnet Id", "VPC Endpoint Id", "VPC Id"},
+	"AWS/PrivateLinkServices":     {"Az", "Load Balancer Arn", "Service Id", "VPC Endpoint Id"},
 	"AWS/RDS":                     {"DBClusterIdentifier", "DBInstanceIdentifier", "DatabaseClass", "DbClusterIdentifier", "EngineName", "ProxyName", "Role", "SourceRegion", "Target", "TargetGroup", "TargetRole"},
 	"AWS/Redshift":                {"ClusterIdentifier", "NodeID", "service class", "stage", "latency", "wlmid"},
 	"AWS/Robomaker":               {"SimulationJobId"},