feat(cli): implement multi-applet binary dispatch and signal handling

crates/irtt-cli/src/shared/client/mod.rs

@@ -0,0 +1,10 @@
+pub mod args;
+pub mod config;
+pub mod session;
+
+pub use args::{
+    parse_dscp, parse_duration, parse_length, parse_server_fill, parse_test_duration, parse_ttl,
+    ClockArg, CommonClientArgs, ReceivedStatsArg, TimestampArg,
+};
+pub use config::{expected_probe_count, DEFAULT_RECV_TIMEOUT};
+pub use session::{final_drain_duration, is_shutdown_requested, ClientSession, RECV_BUDGET};