Call through to ART Service in notifyDexLoad if it is enabled.

Move the ArtManagerLocal initialization to a place where it can access
PackageManagerLocal but still is early enough to precede binder calls
to notifyDexLoad.

Test: Build with dalvik.vm.useartservice=true, boot, launch an app, and
      check with temporary logging that
      ArtManagerLocal.notifyDexContainersLoaded gets called.
Bug: 254043366
Change-Id: I97d59f9c15402648627006dde874a068b0706157