feat(client): implement core echo probe sending and receiving logic

crates/irtt-client/src/lib.rs

@@ -4,13 +4,17 @@ mod client;
 mod config;
 mod error;
 mod event;
+mod probe;
 mod session;
 mod socket;
 mod timing;
 
 pub use client::Client;
-pub use config::{ClientConfig, NegotiationPolicy, RunMode, SocketConfig};
+pub use config::{ClientConfig, NegotiationPolicy, RecvBudget, RunMode, SocketConfig};
 pub use error::ClientError;
-pub use event::{ClientEvent, OpenOutcome};
+pub use event::{
+    ClientEvent, OneWayDelaySample, OpenOutcome, PacketMeta, ReceivedStatsSample, RttSample,
+    ServerTiming,
+};
 pub use session::NegotiatedParams;
 pub use timing::ClientTimestamp;