[Integration Testing Framework] Switch to using Terraform as provisioner

[ycombinator]

Based on the success of @pchila's POC, we've decided to switch to using Terraform as the provisioner for VMs and ESS deployments used by the integration testing framework.

Definition of done

• The integration testing framework provisions Linux VMs using Terraform instead of OGC
• The integration testing framework provisions Windows VMs using Terraform instead of OGC
• The integration testing framework provisions ESS deployments using Terraform instead of directly calling the ESS API

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[rdner]

I suppose the most challenging part will be converting our instance definitions to Terraform ones and feeding them to the tool like we do for OGC

elastic-agent/pkg/testing/ogc/provisioner.go

Lines 287 to 319 in c45842a

	func osBatchToOGC(cacheDir string, batch runner.OSBatch) Layout {
	tags := []string{
	LayoutIntegrationTag,
	batch.OS.Type,
	batch.OS.Arch,
	}
	if batch.OS.Type == define.Linux {
	tags = append(tags, strings.ToLower(fmt.Sprintf("%s-%s", batch.OS.Distro, strings.Replace(batch.OS.Version, ".", "-", -1))))
	} else {
	tags = append(tags, strings.ToLower(fmt.Sprintf("%s-%s", batch.OS.Type, strings.Replace(batch.OS.Version, ".", "-", -1))))
	}
	los, _ := findOSLayout(batch.OS.OS)
	return Layout{
	Name: batch.ID,
	Provider: los.Provider,
	InstanceSize: los.InstanceSize,
	RunsOn: los.RunsOn,
	RemotePath: los.RemotePath,
	Scale: 1,
	Username: los.Username,
	SSHPrivateKey: cacheDir + "/id_rsa",
	SSHPublicKey: cacheDir + "/id_rsa.pub",
	Ports: []string{"22:22"},
	Tags: tags,
	Labels: map[string]string{
	"division": "engineering",
	"org": "platform",
	"team": "ingest",
	"project": "elastic-agent",
	},
	Scripts: "path", // not used; but required by OGC
	}
	}