refactor: remove logical_seq from client events, session tracking and stats usage

It was an attempt at handling integer wraparound more cleanly keeping in mind that we have a continuous mode,
and so we can more easily reach seq > u32::MAX

However after running the numbers, if we run with a interval of 10ms, it's still gonna take ~497 days before we hit integer overflow, so for now it doesn't seem worth to have this extra logic to handle something that'll in 99.9% of cases be purely an edge case

Keeping in mind autorate usage, in sqm-autorate-rust each send loop is 500 ms by default, and the sleep is then 500 ms / 5 reflectors, so our interval is 100 ms. that means it'll take 4970 days or ~13.6 years to reach the limit. Not worth dealing with IMO

crates/irtt-client/tests/hmac.rs

@@ -73,13 +73,11 @@ fn hmac_echo_success_verifies_request_and_accepts_reply() {
     match &run.reply {
         ClientEvent::EchoReply {
             seq,
-            logical_seq,
             bytes,
             server_timing,
             ..
         } => {
             assert_eq!(*seq, 0);
-            assert_eq!(*logical_seq, 0);
             assert_eq!(*bytes, echo_packet_len(true, &params));
             assert!(server_timing.is_some());
         }