Add limitPowerTransfer SystemAPI to UsbPort

limitPowerTransfer when invoked limits the power transfer
in and out of the USB port. limitPortTransfer is deactivated
either when limitPowerTransfer is deactivated by the caller
or when Usb disconnect event is observed by the Usb service.

limitPowerTransfer API is asynchronous and the caller gets
notified by invoking UsbOperationCallback.onUsbOperationComplete
callback to notify the status of the operation.

USB_PORT_CHANGED event is broadcasted when port's limitPowerTransfer
status changes. UsbPortStatus object is updated to reflect the
current status.

limitPowerTransfer is protected by android.permission.MANAGE_USB.

Bug: 199357330
Bug: 199358576
Test: Tested on Pixel
CTS-Coverage-Bug: 215019881
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Change-Id: Iabd1187f7527e14ed758abe355ba94a511d8c859