feat(infrastructure): add the ecs ec2 terraform casting

[Nageshbansal]

Features

• Adds the ecs/ec2/terraform infrastructure casting: a VPC with public and private subnets and their routing, an ECS cluster, node groups per storage class, and the IAM the nodes assume.
• Runs a persistent group as individual instances, each with its own volume mounted at /var/lib/foundry. The ECS agent will not register a node whose volume is not mounted, so a task can never bind onto the root disk.
• Runs an ephemeral group as an autoscaling group behind a launch template.
• Registers each node with the substrate's name and its storage class as ECS instance attributes, which is what an Installation places against.
• Pours cloud-init beside the terraform and references it with filebase64.
• Templates interpolate the derived resources map and assemble no name or tag of their own.
• Adds the example under docs/examples/ecs/ec2/terraform/infrastructure/.

Tests

• Forge tests for the poured set and the cloud-init contents, enricher tests, and template render tests.

Example

apiVersion: v1alpha1
kind: Infrastructure
metadata:
  name: foundry
spec:
  deployment:
    platform: ecs
    mode: ec2
    flavor: terraform
  resource:
    spec:
      config:
        data:
          resource.yaml: |
            networking:
              networkCIDR: 10.0.0.0/16
              subnets:
                private-a:
                  type: private
                  zone: us-east-1a
                  cidr: 10.0.0.0/19
                public-a:
                  type: public
                  zone: us-east-1a
                  cidr: 10.0.96.0/22
            instanceGroups:
              persistent:
                minSize: 3
                maxSize: 3
                machineType: t3.medium
                dataVolume:
                  size: 5
              ephemeral:
                machineType: t3.small
  patches:
    - target: "infrastructure/variables.tf.json"
      type: jsonpatch
      operations:
        - op: replace
          path: /variable/aws_region/default
          value: us-east-1

Related: SigNoz/platform-pod#2743