Add buildbot target using linux_bionic zipapex

Adds art-linux-bionic-x64-zipapex target config. This target uses
binaries from the com.android.runtime.host zipapex to execute the art
run-test suite.

Test: ./test/testrunner/run_build_test_target.py -j72 art-linux-bionic-x64-zipapex
Bug: 120436895
Change-Id: Ie0cb1b7489f698dfb4f7f6d01a4c99701343cfff