Installd: 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.

Also, fix the getUserSize by considering the size of the actual profiles
not of the set of empty markers.

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

Bug: 32871170
Change-Id: I9250e816a1bfa95cb10155e513ae28ebfda7ce4b