Marked apks loaded by isolated processes as usedByOthers

Isolated processes can only access world readable optimized files.
In order to not penalize their execution, we mark any dex files they
load as usedByOthers. This will prevent speed-profile optimizations
which marks the optimized files private to the app process.

Test: DexManagerTests
Bug: 163018062
Change-Id: Ib041584926ea142f37993f434a728d90db30e9bc