Add infrastructure (Terraform) deployment template

Based on https://gitlab.developers.cam.ac.uk/uis/devops/raven/infrastructure/-/merge_requests/41, we should generate a project-generic template for running terraform plan and terraform apply as part of CD, managed via the GitLab Environments page. This should be similar to the Cloud Run deployment template, in particular supporting the use of a SERVICE_PREFIX variable to aid in customisation/duplication of the jobs.

This issue includes resolving whether we should use resource groups or specific pipeline options to improve the robustness of the flow. See https://gitlab.developers.cam.ac.uk/uis/devops/raven/infrastructure/-/merge_requests/41#note_226319