Implement AWS lab

[kalebcastillo]

This pull request introduces full AWS support for the networking lab by adding comprehensive documentation, deployment, validation, and teardown scripts. It transitions the AWS lab from a placeholder to a fully functional, incident-driven exercise, aligning it with the Azure experience. The most important changes are grouped below:

AWS Lab Enablement and Documentation

• Added a detailed aws/README.md describing the AWS networking lab scenario, prerequisites, incident queue, validation workflow, and cleanup process. This provides step-by-step guidance for users to deploy, troubleshoot, and resolve networking issues in AWS.
• Updated the main README.md to mark AWS as available and link to the new AWS guide, reflecting the lab's readiness for learners.
• Revised .github/skills/validate-networking-lab/aws/README.md to remove the "coming soon" notice, document the available scripts, and add the new run-full-validation.sh script. [1] [2]

AWS Automation Scripts

• Added aws/scripts/setup.sh to automate deployment of intentionally broken AWS infrastructure using Terraform, including pre-flight checks, user prompts, and post-deployment instructions.
• Added aws/scripts/destroy.sh to safely tear down all AWS lab resources, clean up Route53 records and SSH keys, and prevent ongoing charges.
• Added aws/scripts/validate.sh, a robust validation script that tests incident resolution by checking real connectivity between VMs, validates security group rules, and generates/verifies completion tokens for learners.

These changes provide a complete, hands-on AWS networking troubleshooting experience, with clear documentation and tooling for deployment, validation, and cleanup.

[rishabkumar7]

Added support for Bash version 3 (macOS). Was able to test the 2 incidents:

❯ ./validate.sh

============================================
Incident Status
============================================
  ✓ INC-4521
  ✓ INC-4522
  ✗ INC-4523
  ✗ INC-4524