Fix ART Service initialization order problems.

- Move ArtManagerLocal initialization before the boot compilation step
  (UpdatePackagesIfNeeded).
- Delay scheduling the background dexopt job because the job scheduler
  hasn't been started at that point.

Test: Boot with dalvik.vm.useartservice=true and check logcat that ART
  Service starts up and a first-boot dexopt runs without errors.
Bug: 266028904
Change-Id: I108b877f2a99c69c20f7209339cd193c2d41e7ea