[UA] Ensure that old indices are detected for reindexing (elastic#203082

)

## Summary

We need to handle the following response shape from `GET
_migration/deprecations`

```jsonc
    "myindex": [
      {
        "level": "critical",
        "message": "Old index with a compatibility version < 8.0", // specifically this message
        "url": "https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking-changes-9.0.html",
        "details": "This index has version: 7.17.25",
        "resolve_during_rolling_upgrade": false
      }
    ]
```

<img width="1142" alt="Screenshot 2024-12-05 at 12 44 59"
src="https://github.com/user-attachments/assets/723e19ab-dd9d-4b6a-bcda-26a5c8bffa0b">


## To reviewers

These changes were developed/tested on `8.x` and must be backported.

Related
* elastic#202669
* elastic/elasticsearch#118062

x-pack/plugins/upgrade_assistant/server/lib/__fixtures__/fake_deprecations.json

@@ -147,6 +147,15 @@
         "details": "[[type: tweet, field: liked]]",
         "resolve_during_rolling_upgrade": false
       }
+    ],
+    "myindex": [
+      {
+        "level": "critical",
+        "message": "Old index with a compatibility version < 8.0",
+        "url": "https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking-changes-9.0.html",
+        "details": "This index has version: 7.17.25",
+        "resolve_during_rolling_upgrade": false
+      }
     ]
   },
   "data_streams": {

x-pack/plugins/upgrade_assistant/server/lib/es_deprecations_status/get_corrective_actions.ts

@@ -20,6 +20,12 @@ type EsMetadata = Actions & {
   [key: string]: string;
 };
 
+// TODO(jloleysens): Replace these regexes once this issue is addressed https://github.com/elastic/elasticsearch/issues/118062
+const ES_INDEX_MESSAGES_REQIURING_REINDEX = [
+  /Index created before/,
+  /index with a compatibility version \</,
+];
+
 export const getCorrectiveAction = (
   message: string,
   metadata: EsMetadata,
@@ -31,7 +37,9 @@ export const getCorrectiveAction = (
   const clusterSettingDeprecation = metadata?.actions?.find(
     (action) => action.action_type === 'remove_settings' && typeof indexName === 'undefined'
   );
-  const requiresReindexAction = /Index created before/.test(message);
+  const requiresReindexAction = ES_INDEX_MESSAGES_REQIURING_REINDEX.some((regexp) =>
+    regexp.test(message)
+  );
   const requiresIndexSettingsAction = Boolean(indexSettingDeprecation);
   const requiresClusterSettingsAction = Boolean(clusterSettingDeprecation);
   const requiresMlAction = /[Mm]odel snapshot/.test(message);