Support vendor GNSS file properties for AAOS virtualization

The Android Automotive trout device uses GNSS HAL for fetching
location data from a live GNSS adapter, not a mock file. We also have
an established naming convention for console port names that is carried
over from the Bluetooth use case.

Add support for a vendor uart port for GNSS in addition to the existing
Cuttlefish debug property, in order to enable trout to establish a
connection to the host GNSS agent

Bug: 213489959
Test: build flash and boot
Change-Id: Id2d2134bb6ea60adef1072295c4f623463bfb010