chore(volo-http): adjust stats of client and server

[wfly1998]

Motivation

We note that process_start, process_end and method, uri, status_code are common information, it is best to put them in CommonStats. And only the client needs to log transport times, so this can be put in ClientStats.

Solution

 pub struct CommonStats {
+    process_start_at: Option<DateTime<Local>>,
+    process_end_at: Option<DateTime<Local>>,
+
+    method: Option<Method>,
+    uri: Option<Uri>,
+    status_code: Option<StatusCode>,
+
     req_size: Option<u64>,
     resp_size: Option<u64>,
-    status_code: Option<StatusCode>,
 }

+pub struct ServerStats {}
-pub struct ServerStats {
-    process_start_at: Option<DateTime<Local>>,
-    process_end_at: Option<DateTime<Local>>,
-
-    method: Option<Method>,
-    uri: Option<Uri>,
-}

 pub struct ClientStats {
     transport_start_at: Option<DateTime<Local>>,
     transport_end_at: Option<DateTime<Local>>,
-
-    status_code: Option<StatusCode>,
 }