add HomeHelperTest to check SystemUI

Test: cd to Master directory, lunch target <hawk-userdebug>
cd frameworks/base/packages/CarSystemUI/src/com/android/systemui
run `atest :auto-end-to-end-postsubmit`
test would fail if SystemUI is broken or any element is missing on
homepage

bug:144112416
Change-Id: I71c61a5361f69a87d91684bf1905b6dc5866e446