feat: Correct server metrics and add more metrics for scan (#3426)

* feat: drop timer on stream terminated

* refactor: combine metrics into a histogram vec

* refactor: frontend grpc metrics

* feat: add metrics middleware layer to grpc server

* refactor: move http metrics layer to metrics mod

* feat: bucket for grpc/http elapsed

* feat: remove duplicate metrics

* style: fix cilppy

* fix: incorrect bucket of promql series

* feat: more metrics for mito

* feat: convert cost

* test: fix metrics test

tests-integration/tests/http.rs

@@ -557,7 +557,8 @@ pub async fn test_metrics_api(store_type: StorageType) {
     let res = client.get("/metrics").send().await;
     assert_eq!(res.status(), StatusCode::OK);
     let body = res.text().await;
-    assert!(body.contains("frontend_handle_sql_elapsed"));
+    // Comment in the metrics text.
+    assert!(body.contains("# HELP"));
     guard.remove_all().await;
 }