test: add terratest infrastructure and module integration tests

[l50]

Key Changes:

• Introduced comprehensive Go-based Terratest suites for module validation
• Added pre-commit hooks to enforce Go formatting and vetting in module tests
• Implemented robust resource cleanup utilities for test isolation
• Integrated Terratest into CI with a dedicated GitHub Actions workflow

Added:

• Terratest test suites for module validation:
  • Created Go test suites under modules/terraform-aws-instance-factory/test and
    modules/terraform-aws-net/test to cover EC2, ASG, storage, and networking
    scenarios with AWS SDK v2 and Terratest.
  • Implemented test helpers for resource creation, subnet discovery, security group
    handling, and output validation.
  • Defined resource cleanup utilities to reliably remove test artifacts (instances,
    ASGs, subnets, security groups, IAM roles/profiles, etc.).
  • Introduced Go module files (go.mod, go.sum) for test dependencies.
• Pre-commit hooks for module test hygiene:
  • Added steps to run gofmt, go vet, and go build on all module test
    directories to enforce code quality.
• Terratest GitHub Actions workflow:
  • Added .github/workflows/terratest.yaml to run Terratest on PRs, pushes,
    schedules, and merge groups.
  • Detects changed modules and runs only relevant tests; supports concurrency
    control and AWS OIDC credentials.

Changed:

• Enhanced syntax-check workflow for environment variable handling and cache key
  precision.
• Updated GoReleaser workflow to only trigger on vX.Y.Z tags, reducing noise.
• Improved meta-labeler workflow with security documentation and warnings against
  unsafe usage.
• Refined pre-commit configuration to include new test-related Go hooks.

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