[Test] add environment variables that is needed by samples (Azure#29665)

to fix samples run in live tests. It would have been nicer if the same
set of variables are used for both tests and samples. However the names
in samples are better customer-facing and this PR is a simple and
straightforward fix.

Author: jeremymeng

sdk/cognitivelanguage/ai-language-conversations/tests.yml

@@ -11,3 +11,10 @@ extends:
         LANGUAGE_CLU_DEPLOYMENT_NAME: $(clu-project-deployment)
         LANGUAGE_ORCHESTRATION_PROJECT_NAME: $(clu-workflow-project)
         LANGUAGE_ORCHESTRATION_DEPLOYMENT_NAME: $(clu-workflow-project-deployment)
+        # The following are for samples
+        AZURE_CONVERSATIONS_ENDPOINT: $(clu-uri)
+        AZURE_CONVERSATIONS_KEY: $(clu-key)
+        AZURE_CONVERSATIONS_PROJECT_NAME: $(clu-project)
+        AZURE_CONVERSATIONS_DEPLOYMENT_NAME: $(clu-project-deployment)
+        AZURE_CONVERSATIONS_WORKFLOW_PROJECT_NAME: $(clu-workflow-project)
+        AZURE_CONVERSATIONS_WORKFLOW_DEPLOYMENT_NAME: $(clu-workflow-project-deployment)