De-duplicate Ambient LED management code

[fifieldt]

We currently have 4 different places where we have the logic for modifying LED state of the various types of Ambient LEDs, ExternalNotificationModule::SetExternalOff
ExternalNotificationModule::SetExternalOn
AmbientLightingThread::setLighting
AmbientLightingThread::setLightingOff

This patch de-duplicates the methods in ExternalNotification to a single method, using a boolean to toggle whether we're turning things on or off.

[fifieldt]

Github diff doesn't make it easy to see: here's past off and on:

[fifieldt]

Where I think this could go next -- make AmbientLighting responsible for LED stuff and call it from ExternalNotification.

[caveman99]

Where I think this could go next -- make AmbientLighting responsible for LED stuff and call it from ExternalNotification.

We are trying to resolve those cross-depencencies of the modules. In principal it is good but can we use the notification system we have in the firmware for IPC. E.G. Ambient lighting offering a subscription service for LED changes and the External Notifications just using it (if available)

You can look at how it's done for notifying others about GPS position changes :-)

[fifieldt]

Thanks, I appreciate the guidance. Shall we merge this one as a start - since it'll be a while before I can get to the next steps?