Use Zuul templates

Use templates instead of individual jobs so that these
can be changed in one place.

Depends-On: https://review.opendev.org/677606
Change-Id: If47727858f1a2bef239be5ec400f4447b09f4722

.zuul.yaml

@@ -2,11 +2,11 @@
 
 - project:
     templates:
-      - build-openstack-docs-pti
+      - publish-stx-docs
+      - stx-api-ref-jobs
+      - stx-release-notes-jobs
     check:
       jobs:
-        - build-openstack-api-ref
-        - build-openstack-releasenotes
         - flock-devstack-fault
         - openstack-tox-linters
         - openstack-tox-pep8
@@ -15,16 +15,9 @@
             voting: false
     gate:
       jobs:
-        - build-openstack-api-ref
-        - build-openstack-releasenotes
         - flock-devstack-fault
         - openstack-tox-linters
         - openstack-tox-pep8
-    post:
-      jobs:
-        - publish-stx-api-ref
-        - publish-stx-tox
-        - publish-stx-releasenotes
 
 # Perform just a build
 - job: