refactor(app): clarify application and binary roles

Rename the application Cargo package from irtt-cli to irtt-rs
(crates/irtt-cli -> crates/irtt-app), and hard-rename its scriptable
client binary from irtt-cli to irtt-client, now that the application
also ships a first-class server and the old name reads as an umbrella
CLI for both roles.

Give each dedicated binary (irtt-client, irtt-tui, irtt-server) its
own entry point instead of funneling through the multicall
dispatcher's argv0/subcommand logic, so a dedicated binary only links
the applet code for the role it implements and always runs that role
regardless of the name it's invoked or copied under. irtt-rs remains
the feature-selectable multicall dispatcher and is now the only binary
that inspects argv0 or subcommands.

Move future application releases to the irtt-rs/vX.Y.Z tag namespace
(regenerated via `dist generate`), and bump the application package to
0.6.0 as a breaking distribution change. Library crate versions are
unaffected.

scripts/run_netem_interop_ci.py

@@ -105,13 +105,13 @@ def parse_args() -> argparse.Namespace:
     )
     parser.add_argument(
         "--irtt-rs-command",
-        default=str(REPO_ROOT / "target" / "debug" / "irtt-cli"),
-        help="Path or command for irtt-rs client (default: target/debug/irtt-cli).",
+        default=str(REPO_ROOT / "target" / "debug" / "irtt-client"),
+        help="Path or command for irtt-rs client (default: target/debug/irtt-client).",
     )
     parser.add_argument(
         "--skip-build",
         action="store_true",
-        help="Do not run cargo build -p irtt-cli before comparisons.",
+        help="Do not run cargo build -p irtt-rs --bin irtt-client before comparisons.",
     )
     parser.add_argument(
         "--sudo",
@@ -176,7 +176,10 @@ def main() -> int:
         upstream_irtt = resolve_command(args.upstream_irtt)
         irtt_rs_command = resolve_irtt_rs_command(args.irtt_rs_command)
         if not args.skip_build:
-            run_checked(["cargo", "build", "-p", "irtt-cli"], run_dir / "cargo-build")
+            run_checked(
+                ["cargo", "build", "-p", "irtt-rs", "--bin", "irtt-client"],
+                run_dir / "cargo-build",
+            )
 
         cleanup(args, quiet=True)
         setup_namespaces(args, run_dir)