Add a native UserHalHelper library.

This library contains helper functions to convert the User HAL reponse
structs to VehiclePropValues and request VehiclePropValues to HAL
structs.

Test: atest android.hardware.automotive.vehicle@2.0-utils-unit-tests
Bug: 150409377
Bug: 167588307

Change-Id: I978b39e2f3ee58eb3b154f507c714ca1ba2d1e3b
Merged-In: I978b39e2f3ee58eb3b154f507c714ca1ba2d1e3b
(cherry picked from commit b33e2abb)