Implement USB Suspend

[JohnAZoidberg]

Behavior:

• Turn off LEDs, LED controller
• Other power saving measures

Questions:

• Will it autosuspend while host is not asleep?
• Can we detect if the CDC-ACM port is open/closed and reduce power if not?
• Should enable or disable remote wakeup?

References:

• https://docs.rs/usbd-serial/latest/usbd_serial/
• https://docs.rs/usb-device/latest/usb_device/device/enum.UsbDeviceState.html
• https://learn.microsoft.com/en-us/windows-hardware/drivers/kernel/device-power-states
• https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/comparing-usb-device-states-to-wdm-device-states
• https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v13.0.0%2Fusbd_cdc_acm_example.html
• linux cdc suspend even when opened hathach/tinyusb#1028
• https://www.kernel.org/doc/Documentation/usb/power-management.txt
• https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/usb-selective-suspend
• https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/remote-wakeup-of-usb-devices
• https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/usb-selective-suspend

[JohnAZoidberg]

Basics done in #58!

[JohnAZoidberg]

We can try to go into D3 sleep state, what we can't do on the keyboard, since the keyboard will have to be able to wake up the system.