Add integration tests for pre-release validation

[marcelovilla]

Context

Implement integration tests that deploy both example configurations (provided networking and IAM resources and automated provisioning) to a real AWS account, verify the clusters are functional, and then clean up resources. Tests should run when merging PRs to main and support manual triggering for developer convenience. The tests will be implemented using terratest.

Value and/or benefit

Catches real-world deployment issues before releases and gives developers an on-demand way to verify their changes work end-to-end without manual testing overhead.

Anything else?

No response