Run package tests with warn-as-error (#5290)

.yamato/com.unity.ml-agents-coverage.yml

             {% if package.name == "com.unity.ml-agents.extensions" %}
             pull_request.changes.any match "com.unity.ml-agents.extensions/**" OR
             {% endif %}
-            pull_request.changes.any match ".yamato/com.unity.ml-agents-test.yml")
+            pull_request.changes.any match ".yamato/com.unity.ml-agents-coverage.yml")
       {% endif %}
 {% endfor %}
 {% endfor %}

.yamato/com.unity.ml-agents-test.yml

         flavor: {{ platform.flavor}}
     commands:
         - npm install upm-ci-utils@stable -g --registry https://artifactory.prd.cds.internal.unity3d.com/artifactory/api/npm/upm-npm
-        - upm-ci project test -u {{ editor.version }} --project-path {{ editor.testProject }} --package-filter {{ package.name }} {{ noDefaultPackagesOptions }} --extra-utr-arg "reruncount=2"
+        - upm-ci package test -u {{ editor.version }} --package-path {{ package.name }} {{ noDefaultPackagesOptions }} --warnings-as-errors --extra-utr-arg "reruncount=2"
     artifacts:
         logs:
             paths: