helm: Add helm chart tests (#20394)

* helm: Fix consistent list indentation

* helm: Add helm lint and helm template tests

* helm: Add helm template --validate test

* helm: Add helm install test

chart/templates/job-db-migrate.yaml

@@ -25,13 +25,13 @@ spec:
       affinity:
         podAffinity:
           requiredDuringSchedulingIgnoredDuringExecution:
-          - labelSelector:
-              matchExpressions:
-                - key: app.kubernetes.io/part-of
-                  operator: In
-                  values:
-                    - rails
-            topologyKey: kubernetes.io/hostname
+            - labelSelector:
+                matchExpressions:
+                  - key: app.kubernetes.io/part-of
+                    operator: In
+                    values:
+                      - rails
+              topologyKey: kubernetes.io/hostname
       {{- end }}
       volumes:
         - name: assets