feat: add Cloudbuild config

[hyunuk]

This PR:

• adds a terraform cloudbuild config file to src/yaml (terraform.cloudbuild.yaml for init/plan/apply, and destroy.cloudbuild.yaml for init/destroy).
• creates terraform steps in setup.sh and destroy.sh to use cloudbuild instead of local terraform

To test:

• Open this link to clone the forked branch in your Cloud Shell and check Trust repo
  • You must be able to log in with the appropriate account. If not, execute gcloud auth login.
• run git checkout cloudbuild
• run ./setup.sh project_id="PROJECT_NAME" region="us-central1" enable_apis=true force_destroy=true. The script will execute in following instructions.
  • Check if terraform.tfvars exists and read project name and region if available.
  • If it exists, get project name and region from the file and store them into variables.
  • If not, create terraform.tfvars file based on parameters.
  • Check if backend.tf exists and create a new one if it isn't. backend.tf file is necessary to set a bucket to store terraform state file.
  • Enable services that are needed to manage resources.
  • Grant IAM permissions to the cloudbuild service account
  • Setup Terraform state bucket
  • Run Cloud build
• after applying, run ./destroy to destroy terraform deployment and revoke permissions.