test(usb): create usb.Controller interface for testing

[mikesmitty]

I mentioned this in a comment on #5109, this is a small refactor of the machine and usb package interactions (and some other changes mixed in that will be created as separate PRs and rebased later on). This creates a usb.Controller interface for use in the USB-related packages for mocking in unit testing and updates machine.USBDev to implement it:

type Controller interface {
	ConfigureUSBEndpoint(desc descriptor.Descriptor, epSettings []EndpointConfig, setup []SetupConfig)
	SendUSBInPacket(ep uint32, data []byte) bool
	AckUsbOutTransfer(ep uint32)
	SendZlp()
	IsInitEndpointComplete() bool
	SetStallEPIn(ep uint32)
	SetStallEPOut(ep uint32)
	ClearStallEPIn(ep uint32)
	ClearStallEPOut(ep uint32)
}

[deadprogram]

@mikesmitty can you please resolve merge conflicts so I can help review. Thank you!