Add network builder and platform APIs (aws#3939)

Added the network builder and platform APIs into the shared library package. Network builder is intended to act as the API to be consumed by the agent to setup networking resources on the host. Network builder invokes the platform APIs to execute platform specific operations like creation of network namespaces etc.

---------

Co-authored-by: Samuel Konat <samjkon@amazon.com>

agent/acs/session/payload_responder.go

@@ -140,7 +140,7 @@ func (pmHandler *payloadMessageHandler) addPayloadTasks(payload *ecsacs.PayloadM
 
 		// Add ENI information to the task struct.
 		for _, acsENI := range task.ElasticNetworkInterfaces {
-			eni, err := ni.ENIFromACS(acsENI)
+			eni, err := ni.InterfaceFromACS(acsENI)
 			if err != nil {
 				pmHandler.handleInvalidTask(task, err, payload)
 				allTasksOK = false

agent/vendor/modules.txt

@@ -44,6 +44,7 @@ github.com/aws/amazon-ecs-agent/ecs-agent/metrics
 github.com/aws/amazon-ecs-agent/ecs-agent/modeltransformer
 github.com/aws/amazon-ecs-agent/ecs-agent/netlib/model/appmesh
 github.com/aws/amazon-ecs-agent/ecs-agent/netlib/model/networkinterface
+github.com/aws/amazon-ecs-agent/ecs-agent/netlib/model/status
 github.com/aws/amazon-ecs-agent/ecs-agent/stats
 github.com/aws/amazon-ecs-agent/ecs-agent/tcs/client
 github.com/aws/amazon-ecs-agent/ecs-agent/tcs/handler

ecs-agent/netlib/common_test.go

@@ -0,0 +1,23 @@
+package netlib
+
+const (
+	taskID             = "random-task-id"
+	eniMAC             = "f0:5c:89:a3:ab:01"
+	eniName            = "f05c89a3ab01"
+	eniMAC2            = "f0:5c:89:a3:ab:02"
+	eniName2           = "f05c89a3ab02"
+	eniID              = "eni-abdf1234"
+	eniID2             = "eni-abdf12342"
+	dnsName            = "amazon.com"
+	nameServer         = "10.1.0.2"
+	nameServer2        = "10.2.0.2"
+	ipv4Addr           = "10.1.0.196"
+	ipv4Addr2          = "10.2.0.196"
+	ipv6Addr           = "2600:1f13:4d9:e611:9009:ac97:1ab4:17d1"
+	ipv6Addr2          = "2600:1f13:4d9:e611:9009:ac97:1ab4:17d2"
+	subnetGatewayCIDR  = "10.1.0.1/24"
+	subnetGatewayCIDR2 = "10.2.0.1/24"
+	netNSNamePattern   = "%s-%s"
+	searchDomainName   = "us-west-2.test.compute.internal"
+	netNSPathDir       = "/var/run/netns/"
+)