ART: Clean up code related to foreign dex use

We simplified the way we track whether or not a dex file is used by
other apps. DexManager in the framework keeps track of the data and we
no longer need file markers on disk.

Test: device boots, foreign dex markers are not created anymore

Bug: 32871170
Change-Id: I5a04d3bba29581dedf05e21b8b20d79afa9b405a