Adds the internal AWS EC2 compute-provider module and its provider contract.

Changes:

• Adds EC2 resources, IAM policies, validation, logging, and bootstrap configuration.
• Adds Linux, Windows, and macOS runner templates.
• Adds trust-policy support and Terraform tests.

Suppressed comments (2)

modules/compute-providers/aws/ec2/templates/user-data.sh:40

• With the -e shebang, a failed upgrade terminates user data at this command, so the retry branch is unreachable. Test the command as the if condition instead.

  dnf upgrade-minimal -y

modules/compute-providers/aws/ec2/control-plane.tf:115

• This standalone legacy-tag statement grants terminate and tag operations across all runner configurations; the later ghr:environment statement is an alternative grant, not an additional restriction. Scope this statement by environment or remove it so one lane's scale-down role cannot modify runners belonging to another lane.

    condition {
      test     = "StringEquals"
      variable = "ec2:ResourceTag/ghr:Application"
      values   = ["github-action-runner"]
    }

• Files reviewed: 30/30 changed files
• Comments generated: 11
• Review effort level: Balanced