add postsubmit tests using test mapping

add HomeHelperTest and NotificationHelperTest to SystemUI folder as post
submit
add NotificationHelperTest to CarSystemUI folder as post submit
Test: cd to frameworks/base/packages/SystemUI, then run `atest
:auto-end-to-end-postsubmit
cd frameworks/base/packages/CarSystemUI, then run `atest
:auto-end-to-end-postsubmit
bug: 150406061

Change-Id: I8185135c3120a662b2ffe86fff4dacdcc8883a29