Build images using buildx plugin and automatically push on main branch

.gitlab/ci/gitaly.images.yml

@@ -1,5 +1,9 @@
 # Used by Gitaly: https://gitlab.com/gitlab-org/gitaly/blob/master/.gitlab-ci.yml
-.gitaly-matrix:
+gitaly:
+  needs: []
+  extends:
+    - .build_and_push
+  stage: deploy-gitaly
   parallel:
     matrix:
       - DEBIAN: ['bullseye']
@@ -8,16 +12,3 @@
         GIT: ['2.33']
         PGBOUNCER: ['1.14', '']
         POSTGRESQL: ['11', '12', '13'] # We only use the postgresql-client
-
-gitaly test:
-  needs: []
-  extends:
-    - .gitaly-matrix
-    - .test_custom
-
-gitaly push:
-  extends:
-    - .gitaly-matrix
-    - .build_and_deploy_custom
-  stage: deploy-gitaly
-  needs: ["gitaly test"]