rename cdc descriptor type
add tusbh_cdc_mounted_isr & tusbh_cdc_unmounted_isr
replace tusbh_cdc_isr by tusbh_cdc_xfer_isr with extra parameter as
- pipe id
- xferred_bytes

host_class_driver_t add xferred_bytes parameter
void (* const isr) (pipe_handle_t, tusb_event_t); -->   void (* const isr) (pipe_handle_t, tusb_event_t, uint32_t);

update hid_host & its tests
complete CDC serial demo (in a quick hacking way)