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.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 */