Move withPackageSettingsSnapshot methods into PackageManagerInternal

For consumers who don't care about blocking package data updates and
only need data at a specific snapshot in time, these methods would
avoid locking PMS during the iteration process.

Bug: 183643808

Test: atest com.android.server.pm.test.verify.domain

Change-Id: Ia951381798d75f77c4ad5fc010a469b69992f074