Always reevaluate whether to show the notification for USB_DEVICE_* intents

The decision whether to show or hide the "Usb supplying power.."
notification is based on two different broadcasts
1. USB_DEVICE_ATTACHED/DETACHED
2. USB_PORT_CHANGED

Depending on how long the port takes to enumerate, the required
intents might arrive in different order. Previously, it was assumed
that the ATTACHED broadcast would arrive before the PORT_CHANGED
broadcast and the code was aggressive to reduce the number of
times the decision to display/hide the notification is made.
This might cause the notification to be displayed in some instances
when it is not supposed to be displayed. This CL makes the usb service
to always reevaluate whenever USB_DEVICE_ATTACHED/DETACHED is
received.

Also, adding logs to print whenever the notification in enqueued/
dequeued.

Bug: 63785369
Test: Verified that the notification is displayed when connecting
to another pixel device and hidden when mouse or headset is
connected.
Change-Id: I30650a2d9923d01a1fce4b9450e65ec7f4e6557b