MM-49984: Displaying active search backend in system console (#22721)

This will be shown in the system console to let users know
which search backend is active.

Implemented via adding an extra param in the ping response.

https://mattermost.atlassian.net/browse/MM-49984

```release-note
The database section in the system console now has an additional
read-only section which shows the active search backend in use.

This can be helpful to confirm which is the currently active
search engine when there are multiple of them configured.
```
---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/i18n/en.json

@@ -7795,6 +7795,10 @@
     "id": "ent.elasticsearch.indexer.index_batch.nothing_left_to_index.error",
     "translation": "Trying to index a new batch when all the entities are completed"
   },
+  {
+    "id": "ent.elasticsearch.max_version.app_error",
+    "translation": "Elasticsearch version {{.Version}} is higher than max supported version of {{.MaxVersion}}"
+  },
   {
     "id": "ent.elasticsearch.not_started.error",
     "translation": "Elasticsearch is not started"
@@ -7863,10 +7867,6 @@
     "id": "ent.elasticsearch.search_users.unmarshall_user_failed",
     "translation": "Failed to decode search results"
   },
-  {
-    "id": "ent.elasticsearch.start.already_started.app_error",
-    "translation": "Elasticsearch is already started."
-  },
   {
     "id": "ent.elasticsearch.start.create_bulk_processor_failed.app_error",
     "translation": "Failed to create Elasticsearch bulk processor."