ART: Retire desugar and dx in run-tests

Run-tests now use d8 for desugaring and dexing.

Build scripts no longer have hand written dexer invocations.

Bug: 110150973
Bug: 73711890
Test: art/test.py --host --64 -r
Test: art/test.py --target --prebuild --optimizing -r
Change-Id: Iae2199cf756624c1f045de7777c5ee6432398bd2