CFT developer-tools docker image still relies on Kitchen tests

The CFT docker image (*cft/developer-tools*) provides an easy to use environment to develop our GCP related modules.

However it seems that the [bundled script](https://github.com/GoogleCloudPlatform/cloud-foundation-toolkit/blob/master/infra/build/developer-tools/build/scripts/test_integration.sh) at `/usr/local/bin/test_integration.sh` still relies on the [Kitchen testing framework](https://github.com/GoogleCloudPlatform/cloud-foundation-toolkit/blob/d3fa12b15432a924e942ed220e825f85f640635d/infra/build/developer-tools/build/scripts/task_helper_functions.sh#L641), while most of the examples you provide in your terraform modume are based on the [blueprint-test framework](https://pkg.go.dev/github.com/GoogleCloudPlatform/cloud-foundation-toolkit/infra/blueprint-test#section-readme) (cft CLI bundled in the image).

Is there any plan to update this script to now rely on CFT rather than kitchen ? I can propose a PR to introduce this change or create a separate script alongside this one to keep retro-compatibility ?