test(client): update test helpers to handle fallible packet length calculations

crates/irtt-client/src/client/tests/mod.rs

@@ -1,8 +1,8 @@
 use super::*;
 use crate::config::{NegotiationPolicy, DEFAULT_OPEN_TIMEOUTS};
 use irtt_proto::{
-    echo_packet_len, flags::FLAG_HMAC, flags::FLAG_OPEN, flags::FLAG_REPLY, verify_hmac, Clock,
-    ReceivedStats, StampAt, HMAC_SIZE, MAGIC,
+    flags::FLAG_HMAC, flags::FLAG_OPEN, flags::FLAG_REPLY, verify_hmac, Clock, ReceivedStats,
+    StampAt, HMAC_SIZE, MAGIC,
 };
 use std::{thread, time::SystemTime};