feat: add support for cancellable hotplug

[erkki-silvola]

Note did not add much docs as I was not sure how much conversation this will raise, also unsure about the naming. This is intended for 'library' use case where hotplug needs to be started and stopped...

[kevinmehall]

I don't think you need special support in nusb for this -- if you drop the HotplugWatch, it will clean itself up. You can do the rest externally with select or or from several different async libraries, and a oneshot channel or signal directly. You've effectively re-implemented that. I don't think every library that provides a Stream needs to re-implement their own version of cancellation, because the power of the Future and Stream traits is that they are composable.

[erkki-silvola]

I don't think you need special support in nusb for this -- if you drop the HotplugWatch, it will clean itself up. You can do the rest externally with select or or from several different async libraries, and a oneshot channel or signal directly. You've effectively re-implemented that. I don't think every library that provides a Stream needs to re-implement their own version of cancellation, because the power of the Future and Stream traits is that they are composable.

Yes, sorry for this, still a bit new on this, used stream abortable which effectively is the same