Loki: Show query size approximation (#62109)

* feat: make api request to /loki/api/v1/index/stats

* fix: add /index/stats to callResource valid urls

* feat: make call to getQueryStats when the query changes

* feat: render user tooltip displaying the estimated value for processed data

* fix: add new props to component tests

* test: add tests for query size estimation

* fix: disable error message on request failure

* refactor: add suggestions from code review

* refactor: only pass required query string

pkg/tsdb/loki/loki.go

@@ -112,7 +112,8 @@ func callResource(ctx context.Context, req *backend.CallResourceRequest, sender
 	}
 	if (!strings.HasPrefix(url, "labels?")) &&
 		(!strings.HasPrefix(url, "label/")) && // the `/label/$label_name/values` form
-		(!strings.HasPrefix(url, "series?")) {
+		(!strings.HasPrefix(url, "series?")) &&
+		(!strings.HasPrefix(url, "index/stats?")) {
 		return fmt.Errorf("invalid resource URL: %s", url)
 	}
 	lokiURL := fmt.Sprintf("/loki/api/v1/%s", url)