convert BUILD_CTS_SUPPORT_PACKAGE in mk files

1. Modified the logic of the androidmk tool, to convert the BUILD_CTS_SUPPORT_PACKAGE
field to the android_test_helper_app module type rather than android_test;
2. Updated the unit tests as well.

Bug: 191907322
Test: m androidmk
Test: TreeHugger
Change-Id: Iabff299f6d043521481ef1af457c708353559823