Fix some tests for dexpreopt and remove unnecessary tests.

This CL is to prepare for the changes in http://r.android.com/2652081.
See the description of that CL for the reasons.

Some tests were set up in a fragile way and were easy to be broken when
the implementation changes. This CL is a pure test change that fixes
them.

This CL also removes TestNoUpdatableJarsInBootImage. That test checks
what should go to the ART boot image and what should go to the
platform one, which does not apply today because boot images are not
associated with mainline modules anymore: a boot image may take jars
from multiple mainline modules and the platform, and a mainline module
can contribute to multiple boot images. In practice, we have ART jars in
the platform boot image, and we are going to add core-icu4j and
consrypt to the ART boot image, which is now for testing only.

Bug: 290583827
Test: m nothing
Change-Id: I22c45cbf6f853b030b68edb51197854e9c53a02e