Add more context for Watchman/Eden rage log message

Summary:
Looked at Scuba to see if Watchman/Eden rage log upload is working as expected. Realized that I didn't add any contexts other than the link to logs.

I know what the links are since I added them, but it's probably not obvious to other people, so clarifying it a bit

Reviewed By: samkevich

Differential Revision: D68843933

fbshipit-source-id: 5c550a2b5346c5a235e48ef225bad59db7c976df

app/buck2_file_watcher/src/watchman/core.rs

@@ -252,9 +252,12 @@ async fn get_watchman_eden_error_logs() -> Option<String> {
     let (watchman_cmd, eden_cmd) = tokio::join!(watchman_cmd, eden_cmd);
 
     match (watchman_cmd, eden_cmd) {
-        (Some(watchman_cmd), Some(eden_cmd)) => Some(format!("{}\n{}", watchman_cmd, eden_cmd)),
-        (Some(watchman_cmd), None) => Some(watchman_cmd),
-        (None, Some(eden_cmd)) => Some(eden_cmd),
+        (Some(watchman_cmd), Some(eden_cmd)) => Some(format!(
+            "Watchman and Eden rage logs:\n{}\n{}",
+            watchman_cmd, eden_cmd
+        )),
+        (Some(watchman_cmd), None) => Some(format!("Watchman rage logs:\n{}", watchman_cmd)),
+        (None, Some(eden_cmd)) => Some(format!("Eden rage logs:\n{}", eden_cmd)),
         (None, None) => None,
     }
 }