Add offline runners info in the Slack report (#19169)

* send slack report for offline runners

Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

utils/notification_service.py

@@ -397,8 +397,12 @@ class Message:
             ci_title_block = {"type": "section", "text": {"type": "mrkdwn", "text": ci_title}}
             blocks.append(ci_title_block)
 
+        offline_runners = []
         if runner_not_available:
             text = "💔 CI runners are not available! Tests are not run. 😭"
+            result = os.environ.get("OFFLINE_RUNNERS")
+            if result is not None:
+                offline_runners = json.loads(result)
         elif runner_failed:
             text = "💔 CI runners have problems! Tests are not run. 😭"
         elif setup_failed:
@@ -413,11 +417,18 @@ class Message:
                 "text": text,
             },
         }
+
+        text = ""
+        if len(offline_runners) > 0:
+            text = "\n  • " + "\n  • ".join(offline_runners)
+            text = f"The following runners are offline:\n{text}\n\n"
+        text += "🙏 Let's fix it ASAP! 🙏"
+
         error_block_2 = {
             "type": "section",
             "text": {
                 "type": "plain_text",
-                "text": "🙏 Let's fix it ASAP! 🙏",
+                "text": text,
             },
             "accessory": {
                 "type": "button",