GTest functional tests that include parameters and uORB messaging (#12521)

* Add kdevelop to gitignore

* Add test stubs

* Rename px4_add_gtest to px4_add_unit_gtest

* Add infrastructure to run functional tests

* Add example tests with parameters and uorb messages

* Fix memory issues in destructors in uORB manager and CDev

* Add a more real-world test of the collision prevention

src/lib/cdev/CDev.cpp

@@ -395,4 +395,27 @@ CDev::remove_poll_waiter(px4_pollfd_struct_t *fds)
 	return -EINVAL;
 }
 
+int CDev::unregister_driver_and_memory()
+{
+	int retval = PX4_OK;
+
+	if (_registered) {
+		unregister_driver(_devname);
+		_registered = false;
+
+	} else {
+		retval = -ENODEV;
+	}
+
+	if (_devname != nullptr) {
+		free((void *)_devname);
+		_devname = nullptr;
+
+	} else {
+		retval = -ENODEV;
+	}
+
+	return retval;
+}
+
 } // namespace cdev

src/lib/cdev/CDev.hpp

@@ -264,6 +264,17 @@ protected:
 
 	px4_sem_t	_lock; /**< lock to protect access to all class members (also for derived classes) */
 
+
+	/**
+	* First, unregisters the driver. Next, free the memory for the devname,
+	* in case it was expected to have ownership. Sets devname to nullptr.
+	*
+	* This is only needed if the ownership of the devname was passed to the CDev, otherwise ~CDev handles it.
+	*
+	* @return  PX4_OK on success, -ENODEV if the devname is already nullptr
+	*/
+	int unregister_driver_and_memory();
+
 private:
 	const char	*_devname{nullptr};		/**< device node name */