sentry: Switch to using Sentry spans for message send timings.

web/src/echo.js

@@ -92,6 +92,7 @@ function resend_message(message, $row) {
     // Always re-set queue_id if we've gotten a new one
     // since the time when the message object was initially created
     message.queue_id = page_params.queue_id;
+    message.resend = true;
 
     const local_id = message.local_id;
 
@@ -115,7 +116,6 @@ function resend_message(message, $row) {
         blueslip.log("Manual resend of message failed");
     }
 
-    sent_messages.start_resend(local_id);
     transmit.send_message(message, on_success, on_error);
 }
 
@@ -400,6 +400,7 @@ export function process_from_server(messages) {
             // the "main" codepath that doesn't have to id reconciliation.
             // We simply return non-echo messages to our caller.
             non_echo_messages.push(message);
+            sent_messages.report_event_received(local_id);
             continue;
         }
 
@@ -413,6 +414,7 @@ export function process_from_server(messages) {
             client_message.content = message.content;
             sent_messages.mark_disparity(local_id);
         }
+        sent_messages.report_event_received(local_id);
 
         message_store.update_booleans(client_message, message.flags);