usb: unify ControlHandler+DeviceStateHandler, route all control requests to all handlers.

- Allows classes to handle vendor requests.
- Allows classes to use a single handler for multiple interfaces.
- Allows classes to access the other events (previously only `reset` was available).

embassy-usb/build.rs

@@ -7,6 +7,7 @@ static CONFIGS: &[(&str, usize)] = &[
     // BEGIN AUTOGENERATED CONFIG FEATURES
     // Generated by gen_config.py. DO NOT EDIT.
     ("MAX_INTERFACE_COUNT", 4),
+    ("MAX_HANDLER_COUNT", 4),
     // END AUTOGENERATED CONFIG FEATURES
 ];