feat: add initial tofu image

Closes #114 (closed)

Summary:

• Docker changes:
  • Renamed existing Dockerfile to Dockerfile.terraform to differentiate it
  • Created new Dockerfile.tofu for the new image. This uses the apk repository to install tofu, so it's much easier than the old TF image that required a manual download.
• gitlab-terraform utility script
  • There's a very small change in this script. The script makes a check to determine which version of terraform is being run by reading the output of terraform -version and parsing the output. This doesn't work with tofu since the output is different, but luckily it doesn't matter since the version check is so old. I added a check if tofu is on the path, and essentially skip the check if it is.
• CI/CD changes
  • There are a LOT of large file changes here, but most of it is copy/paste so it looks deceptively large.
  • The main change here is I removed the "unit" tests from the main CI/CD file and moved them into .gitlab/terraform-test.gitlab-ci.yml to make it much easier to read. This was then effectively copied into tofu-test.gitlab-ci.yml with a lot of the outputs and images changed to ensure they are testing the right output.
  • Example: tofu-test-without-implicit-init expects error text, which needs to be changed from the terraform test since it expects different test output.