Add CLI tests for basic soak testing

This is in no way a complete test suite but is intended as a starting point to get minimal
test coverage for CLI handling tests in. This is necessary to QA the CLI handling
(e.g. removal of commands) and to ensure that we are exercising these code paths in
stack check and alike tests.

src/systemcmds/tests/CMakeLists.txt

@@ -73,6 +73,7 @@ set(srcs
 	test_uart_loopback.c
 	test_uart_send.c
 	test_versioning.cpp
+	test_cli.c
 	tests_main.c
 	)