fix: show tf plan errors in github actions output

[pb-dod]

Fixes: https://github.com/terraform-google-modules/terraform-example-foundation/issues/1109

This PR addresses the lack of detailed error outputs for Terraform plan_validate_all failures within our GitHub Actions, which previously necessitated running plans locally to diagnose issues.

This changes tf-wrapper.sh to capture and display detailed error information from plan_validate_all directly in the GitHub Actions logs, removing the need for local execution to identify errors.

This allows immediate visibility into Terraform plan failures within the CI pipeline and reduces diagnostic time for issues detected during automated Terraform plan validations.

[google-cla[bot]]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[github-actions[bot]]

This PR is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 7 days