Update ES template strings (#29209)

Use a template variable to distinguish between Elasticsearch
and Opensearch
```release-note
NONE
```

server/i18n/en.json

@@ -7631,63 +7631,63 @@
   },
   {
     "id": "ent.elasticsearch.aggregator_worker.create_index_job.error",
-    "translation": "Elasticsearch aggregator worker failed to create the indexing job"
+    "translation": "{{.Backend}} aggregator worker failed to create the indexing job"
   },
   {
     "id": "ent.elasticsearch.aggregator_worker.delete_indexes.error",
-    "translation": "Elasticsearch aggregator worker failed to delete the indexes"
+    "translation": "{{.Backend}} aggregator worker failed to delete the indexes"
   },
   {
     "id": "ent.elasticsearch.aggregator_worker.get_indexes.error",
-    "translation": "Elasticsearch aggregator worker failed to get indexes"
+    "translation": "{{.Backend}} aggregator worker failed to get indexes"
   },
   {
     "id": "ent.elasticsearch.aggregator_worker.index_job_failed.error",
-    "translation": "Elasticsearch aggregator worker failed due to the indexing job failing"
+    "translation": "{{.Backend}} aggregator worker failed due to the indexing job failing"
   },
   {
     "id": "ent.elasticsearch.create_client.ca_cert_missing",
-    "translation": "Could not open the CA file for Elasticsearch"
+    "translation": "Could not open the CA file for {{.Backend}}"
   },
   {
     "id": "ent.elasticsearch.create_client.client_cert_malformed",
-    "translation": "Decoding of the client certificate for Elasticsearch failed"
+    "translation": "Decoding of the client certificate for {{.Backend}} failed"
   },
   {
     "id": "ent.elasticsearch.create_client.client_cert_missing",
-    "translation": "Could not open the client certificate file for Elasticsearch"
+    "translation": "Could not open the client certificate file for {{.Backend}}"
   },
   {
     "id": "ent.elasticsearch.create_client.client_key_missing",
-    "translation": "Could not open the client key file for Elasticsearch"
+    "translation": "Could not open the client key file for {{.Backend}}"
   },
   {
     "id": "ent.elasticsearch.create_client.connect_failed",
-    "translation": "Setting up Elasticsearch Client Failed"
+    "translation": "Setting up {{.Backend}} Client Failed"
   },
   {
     "id": "ent.elasticsearch.create_template_channels_if_not_exists.template_create_failed",
-    "translation": "Failed to create Elasticsearch template for channels"
+    "translation": "Failed to create {{.Backend}} template for channels"
   },
   {
     "id": "ent.elasticsearch.create_template_file_info_if_not_exists.template_create_failed",
-    "translation": "Failed to create Elasticsearch template for files"
+    "translation": "Failed to create {{.Backend}} template for files"
   },
   {
     "id": "ent.elasticsearch.create_template_posts_if_not_exists.template_create_failed",
-    "translation": "Failed to create Elasticsearch template for posts"
+    "translation": "Failed to create {{.Backend}} template for posts"
   },
   {
     "id": "ent.elasticsearch.create_template_users_if_not_exists.template_create_failed",
-    "translation": "Failed to create Elasticsearch template for users"
+    "translation": "Failed to create {{.Backend}} template for users"
   },
   {
     "id": "ent.elasticsearch.data_retention_delete_indexes.delete_index.error",
-    "translation": "Failed to delete Elasticsearch index"
+    "translation": "Failed to delete {{.Backend}} index"
   },
   {
     "id": "ent.elasticsearch.data_retention_delete_indexes.get_indexes.error",
-    "translation": "Failed to get Elasticsearch indexes"
+    "translation": "Failed to get {{.Backend}} indexes"
   },
   {
     "id": "ent.elasticsearch.delete_channel.error",