d/purism-ci.yml: Use pipeline job templates

debian/purism-ci.yml

 include:
  - 'https://source.puri.sm/Librem5/librem5-ci/raw/master/librem5-pipeline-definitions.yml'
+ - 'https://source.puri.sm/Librem5/librem5-ci/raw/master/librem5-pipeline-amber-jobs.yml'
+ - 'https://source.puri.sm/Librem5/librem5-ci/raw/master/librem5-pipeline-common-jobs.yml'
 
 stages:
  - package
  - test-package
 
-variables:
-  L5_DOCKER_IMAGE: debian:buster
-
-package-debian-buster:
-  extends: .l5-build-debian-package
-
-package-debian-buster:arm64:
-  tags:
-    - librem5:arm64
-  extends: .l5-build-debian-package
-
-autopkgtest-debian-buster-package:
-  dependencies:
-    - package-debian-buster
-  extends: .l5-autopkgtest-debian-package
-
-lintian-debian-buster-package:
-  dependencies:
-    - package-debian-buster
-  extends: .l5-lintian-debian-package