Add the D-Bus API definition and its implementation in the form of a GPIO
manager daemon and a companion command-line client as well as some
additional configuration and data files (systemd service, example udev
configuration, etc.) and test suites.

Tested-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Link: https://lore.kernel.org/r/20240812-dbus-v5-4-ead288509217@linaro.org


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>