Revert^2 "Boot image extension."

This reverts commit 9f459c4ef60d771fc4eb8da1f709f479ca23a6ab.

Fixed the extension test to be more hermetic. Added a clean
spec to work around broken dependencies; obsolete images may
have been a reason for boot time regressions.

Test: aosp_taimen-userdebug boots.
Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing --jit
Bug: 119800099
Bug: 143492855
Change-Id: I37e714d53e66f94f791e6d1e9f4d78bf7bcb2116
10 files changed