embassy-usb: Consider an "is_enabled()" method for endpoints?

[jamesmunns]

Sometimes, it is useful to check and see if an endpoint is active prior to doing something like expensive formatting.

Right now, there is only "wait for enabled", and in cases like #3426 there's no feedback when the endpoint is completely down.

it would be nice to have a fn/async fn that doesn't wait for the status, but at least gives a hint whether we expect the Endpoint to be currently active