Update CI to use new components [el9-testing]

This MR implements Update el9-testing branch to new CI/CD component (#15 - closed).

.gitlab/ci/build.yml

-# ---------------------------
-# Build workflow
-# ---------------------------
-
-include:
-  # https://computing.docs.ligo.org/gitlab-ci-templates/
-  - project: computing/gitlab-ci-templates
-    # https://computing.docs.ligo.org/gitlab-ci-templates/docker/
-    file: docker.yml
-  # https://docs.gitlab.com/ee/user/application_security/container_scanning/
-  - template: Security/Container-Scanning.gitlab-ci.yml
-
-# -- build the image --------
-
-build:
-  stage: build
-  extends:
-    # https://computing.docs.ligo.org/gitlab-ci-templates/docker/#.docker:build
-    - .docker:build
-  variables:
-    # use the branch name as the tag
-    CI_REGISTRY_TAG: '$CI_COMMIT_REF_SLUG'
-
-# -- scan the image ---------
-
-# check the image for vulnerabilities, see
-# https://docs.gitlab.com/ee/user/application_security/container_scanning/
-container_scanning:
-  stage: scan
-  needs: [build]
-  variables:
-    DOCKER_IMAGE: '$CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG'
-
-# -- push the image ---------
-
-.push:
-  stage: deploy
-  needs: [build]
-  variables:
-    # pull the branch image
-    PULL_IMAGE: "$CI_REGISTRY_IMAGE:$CI_COMMIT_REF_SLUG"
-    # push to igwn namespace
-    PUSH_IMAGE: "igwn/$CI_PROJECT_NAME:$CI_COMMIT_REF_SLUG"
-  rules:
-    # only run on pushes to the upstream repo (not on forks)
-    - if: '$CI_PROJECT_NAMESPACE == "docker" && $CI_COMMIT_BRANCH'
-
-push:docker_io:
-  extends:
-    # https://computing.docs.ligo.org/gitlab-ci-templates/docker/#.docker:push:docker_io
-    - .docker:push:docker_io
-    - .push
-
-push:quay_io:
-  extends:
-    # https://computing.docs.ligo.org/gitlab-ci-templates/docker/#.docker:push:quay_io
-    - .docker:push:quay_io
-    - .push