Function xmtp_device_sync_sync_all 

pub unsafe extern "C" fn xmtp_device_sync_sync_all(
    client: *const XmtpFfiClient,
    out_synced: *mut i32,
    out_eligible: *mut i32,
) -> i32

Manually sync all device sync groups. Writes the number of synced/eligible groups to the output pointers.