Add native Zuul v3 build and publishing jobs

The new jobs replace (and move in-tree):
- legacy-sahara-extra-artifacts
- legacy-post-sahara-extra-artifacts

Unfortunately the new publish job can't be tested
beforehand, but we can fix it later.

Story: 2001686
Task: 8660

Depends-On: https://review.openstack.org/581087
Change-Id: I5b1ad485dfb23ce164473569b6bbc77fb37871ac

.zuul.yaml

@@ -0,0 +1,33 @@
+- project:
+    check:
+      jobs:
+        - sahara-extra-build-artifacts
+    gate:
+      jobs:
+        - sahara-extra-build-artifacts
+    post:
+      jobs:
+        - sahara-extra-publish-artifacts
+
+- job:
+    name: sahara-extra-build-artifacts
+    description: |
+      Build the artifacts used by Sahara clusters and jobs.
+    parent: unittests
+    timeout: 3600
+    required-projects:
+      - openstack/sahara-extra
+    run: playbooks/build-artifacts/run.yaml
+
+- job:
+    name: sahara-extra-publish-artifacts
+    description: |
+      Build the artifacts used by Sahara clusters and jobs
+      and publish them on tarballs.openstack.org
+    parent: publish-openstack-artifacts
+    timeout: 3600
+    final: true
+    required-projects:
+      - openstack/sahara-extra
+    run: playbooks/build-artifacts/run.yaml
+    post-run: playbooks/build-artifacts/post.yaml

playbooks/build-artifacts/post.yaml

@@ -0,0 +1,14 @@
+- hosts: all
+  name: Copy artifacts
+  tasks:
+    - synchronize:
+        dest: "{{ zuul.executor.work_root }}/artifacts/"
+        mode: pull
+        src: "{{ ansible_user_dir }}/dist"
+        copy_links: true
+        verify_host: true
+        rsync_opts:
+          - --include=/dist/**
+          - --include=*/
+          - --exclude=*
+          - --prune-empty-dirs

playbooks/build-artifacts/run.yaml

@@ -0,0 +1,6 @@
+- hosts: all
+  tasks:
+    - name: Run tools/build-all-artifacts.sh
+      command: bash -xe tools/build-all-artifacts.sh '{{ zuul.branch }}'
+      args:
+        chdir: '{{ zuul.project.src_dir }}'