Add --cdex-fast and --cdex-none variant to testrunner

Added --cdex-fast and --cdex-none variant options. These are passed
to ART through the compact-dex-level option.

Bug: 63756964
Test: test/testrunner/testrunner.py --host --cdex-fast -j40
Test: Commented out header writing in compact_dex_writer.cc and confirmed tests fail.

Change-Id: I408555b48286d2c4c5eca72e2cabe956aa1e9835
4 files changed