feat: use broadcast channel for event listeners (#8193)

Co-authored-by: Emilia Hane <elsaemiliaevahane@gmail.com>

bin/reth/src/commands/import.rs

@@ -257,7 +257,7 @@ where
 
     let max_block = file_client.max_block().unwrap_or(0);
 
-    let mut pipeline = Pipeline::builder()
+    let pipeline = Pipeline::builder()
         .with_tip_sender(tip_tx)
         // we want to sync all blocks the file client provides or 0 if empty
         .with_max_block(max_block)