gpio_controller fix

[Nibanovic]

gpio controller won't compile with C++17 due to this type:

std::atomic<std::shared_ptr<std::string>> target_configuration_;

std_shared does nto have a trivial copy constructor which can be handled with C++17 atomic.
In this PR, I've opted for using realtime_tools::RealtimeThreadSafeBox for access to the string.

COLCON_INGORE io_gripper_controller

Consider deleting io_gripper_controller from the repo, it is empty and this replaces it.

[mergify]

@Nibanovic, all pull requests must be targeted towards the master development branch.
Once merged into master, it is possible to backport to io_gripper_controller, but it must be in master
to have these changes reflected into new distributions.

[mergify]

This pull request is in conflict. Could you fix it @Nibanovic?