Function update_peer_cache_once 

pub async fn update_peer_cache_once(
    config: &Config,
    address_book_service: &mut Buffer<BoxService<AddressBookRequest, AddressBookResponse, BoxError>, AddressBookRequest>,
) -> Result<bool>

Caches the current cacheable peers to disk, based on config.

Returns true if the cache was written, and false if the cacheable peer list was empty, keeping any previous cache.