Wire up DomainVerificationService to PackageManagerService

Sets up the callback and the actual service initialization so that
future domain verification changes can access PackageManager APIs.

Exempt-From-Owner-Approval: Already approved by owners on main branch

Bug: 163565712

Test: none, device boots, tested implicitly as part of other changes

Change-Id: Ie75ad0ee002ae92c21387777ff41c2504c69b836