Implement native TestClient shell

programs/src/bin/test_client.rs

@@ -1,5 +1,3 @@
 fn main() -> std::process::ExitCode {
-    let command_count = libremetaverse_programs::commands::TEST_CLIENT_COMMANDS.len();
-    eprintln!("TestClient command inventory contains {command_count} translated targets");
-    libremetaverse_programs::pending_program("TestClient")
+    libremetaverse_programs::test_client::main_entry()
 }