Move ART tests to use D8.

Because of b/68406220, env.py is not picking soong build vars.
This CL should fix the issue by using USE_D8 and the workaround
checked into build/core/.

This CL also included build file changes to hold a few more checker
tests to continue to use DX temporary until we finish re-writing them.

Bug: 65168732
Test: art/test.py -j20 --host -b
Change-Id: Icc487984c5a1ec4bab94b8e635566c219d0d024b