Support class unloading in dex2oat for quicken multidex

Support class unloading for the quicken compilation filter. This will
be enabled in a follow up CL.

Added a test that compares with and without unloading. The way that
it tests this is by adding an output app image. Having an app image
disables the unloading. This test also covers that app images don't
change the odex (currently).

Added a test for the assumed verified logic.

Bug: 63467744
Test: test-art-host
Test: test/testrunner/testrunner.py --interpreter --host -j40
Change-Id: I1e8a862c6f089c06c58aa0c846797e4c24bd072c