MM-56876: Redis: first introduction (#27752)

```release-note
NONE
```

---------

Co-authored-by: Jesús Espino <jespinog@gmail.com>
Co-authored-by: Mattermost Build <build@mattermost.com>

server/einterfaces/metrics.go

@@ -62,6 +62,7 @@ type MetricsInterface interface {
 	ObserveFilesSearchDuration(elapsed float64)
 	ObserveStoreMethodDuration(method, success string, elapsed float64)
 	ObserveAPIEndpointDuration(endpoint, method, statusCode, originClient, pageLoadContext string, elapsed float64)
+	ObserveRedisEndpointDuration(cacheName, operation string, elapsed float64)
 	IncrementPostIndexCounter()
 	IncrementFileIndexCounter()
 	IncrementUserIndexCounter()