ci: Add support for CentOS 9 Stream on upstream CI.

This patch adds support for running upstream tests using Centos-9
stream images. Both pull request and nightly tests are updated.

tests/azure/azure-pipelines.yml

@@ -18,6 +18,17 @@ stages:
       scenario: fedora-latest
       ansible_version: ">=2.9,<2.10"
 
+# CentOS 9
+
+- stage: CentOS9_Ansible_2_9
+  dependsOn: []
+  jobs:
+  - template: templates/group_tests.yml
+    parameters:
+      build_number: $(Build.BuildNumber)
+      scenario: centos-9
+      ansible_version: ">=2.9,<2.10"
+
 # CentOS 8
 
 - stage: CentOS8_Ansible_2_9