Add option to "Enable USB"

Under the updated flow, the user is given an option to re-enable
USB port and disable contaminant detection until the next unplug
of the USB accessory.

Also, display a Toast message conveying that the USB port has
been re-enabled.

Bug: 128534822
Test: Tested with the mock circuit.
Change-Id: Ifd0a6658a443ae8966ae9128a20e827ed5b03380