Record dex files users in the dex-usage list

Add the users of the dex files in the package-dex-usage.list. This will
provide more data on why a package is marked as shared and not optimized
using profiles.

Test: runtest -x .../DexManagerTests.java
      users of the dex files are recorded in package-dex-usage.list

Bug: 63778376
Change-Id: I329bc929b17fa0afe1531f3e6879f6160157a787