To avoid leaking IPackageManager methods directly into PackageManagerService, moves the IPM implementation into an inner class similar to PackageManagerInternal. This will help enforce snapshot consistency by ensuring that all non-IPM PMS methods can always take in a Computer instance to re-use. Bug: 217961172 Test: presubmit Change-Id: Ibf7bd3d1d90a40786279763ba8d62eb9348bb760