Update Terraform/Base.latest.gitlab-ci.yml to inline cd TF_ROOT

At present this template appears to be designed to never interfere with
other jobs in your CI YML. This is true for all cases except the global
`before_script` which will cause other jobs in your `.gitlab-ci.yml` to
possibly end up in the wrong directory. This was specifically important
for a use case where a project was using terraform and ansible in
https://gitlab.com/gitlab-org/quality/gitlab-environment-toolkit . The
simplest solution appears to be to just inline the `cd ${TF_ROOT}`. We
also considered defining another hidden job that is extended by all the
other jobs here but the indirection didn't seem worth it for a single
step.

changelogs/unreleased/terraform-base-avoid-before-script.yml

+---
+title: Make Terraform/Base.latest.gitlab-ci.yml template safer to use in projects that have non-terraform jobs
+merge_request: 47254
+author:
+type: changed

lib/gitlab/ci/templates/Terraform/Base.latest.gitlab-ci.yml

@@ -12,9 +12,6 @@
 image:
   name: registry.gitlab.com/gitlab-org/terraform-images/stable:latest
 
-before_script:
-  - cd ${TF_ROOT}
-
 variables:
   TF_ROOT: ${CI_PROJECT_DIR}
 
@@ -26,16 +23,19 @@ cache:
 .init: &init
   stage: init
   script:
+    - cd ${TF_ROOT}
     - gitlab-terraform init
 
 .validate: &validate
   stage: validate
   script:
+    - cd ${TF_ROOT}
     - gitlab-terraform validate
 
 .build: &build
   stage: build
   script:
+    - cd ${TF_ROOT}
     - gitlab-terraform plan
     - gitlab-terraform plan-json
   artifacts:
@@ -47,6 +47,7 @@ cache:
 .deploy: &deploy
   stage: deploy
   script:
+    - cd ${TF_ROOT}
     - gitlab-terraform apply
   when: manual
   only: