feat(engine): add tx_index to execute tx span (#22972)

Co-authored-by: Alexey Shekhirin <5773434+shekhirin@users.noreply.github.com>

crates/engine/tree/src/tree/payload_validator.rs

@@ -1009,6 +1009,7 @@ where
             let _enter = debug_span!(
                 target: "engine::tree",
                 "execute tx",
+                tx_index = senders.len() - 1,
             )
             .entered();
             trace!(target: "engine::tree", "Executing transaction");