Function scan 

pub async fn scan<'d>(
    stack: &Stack<'_, Controller<'d>, DefaultPacketPool>,
    duration: Duration,
    on_advertisement: impl FnMut(&Advertisement<'_>),
) -> Result<(), HostError>

Scans for duration, calling on_advertisement for every report (duplicates included, so signal strength stays current). Active scanning, 100 ms interval and window, so names usually arrive too.

Runs the host while scanning; nothing else can use stack meanwhile.