Refactoring CarAudioZoneHelper to be easier to test

Replaced constructor with one that takes an InputStream to make it
easier for tests to provide their own test data

Bug: 131769909
Test: built and ran on device, verified dumpsys matched config xml
Change-Id: I2dac47d71fdaeaa159a9a7a5a00c15d83243e6cf
3 files changed