[Aider assisted]: Templatize rest of the elasticsearch translation strings (#29582)

After https://github.com/mattermost/mattermost/pull/29209, there were some more
strings which were left out. Sending another PR to fix all of them.

The config validation strings are made generic for simplicity, because they
are called before the search backend is started, and even though you could
check for the config setting, it forces the code order. Therefore, changed
the words to just say "Search" for simplicity.

I tried to use Aider initially for a little while, but ended up fighting
a lot with the search/replace and having to repeat myself over and over again
to get it to do the refactoring. Eventually gave up and did rest of the changes
myself.

```release-note
NONE
```

server/enterprise/elasticsearch/opensearch/indexing_job.go

@@ -35,7 +35,7 @@ func (esi *OpensearchIndexerInterfaceImpl) MakeWorker() model.Worker {
 		return nil
 	}
 
-	return common.NewIndexerWorker(workerName,
+	return common.NewIndexerWorker(workerName, model.ElasticsearchSettingsOSBackend,
 		esi.Server.Jobs,
 		logger,
 		esi.Server.Platform().FileBackend(),