Since didSend and didFailToSend are part of the same enum as the command
send actions types, we have to filter them out when subscribing to the
send actions.
This is the beginning of the BLE Pybricks service implementation, so
changes are made to get a handle to the Pybricks control characteristic
and enable notifications.
Currently, only one event (the status report event) and no commands are
implemented on this characteristic.
The new status report event replaces monitoring the UART for >>>>
strings to get the current hub state.
Also includes some minor cleanup in the ble-uart/actions for consistency.
David Lechner