Implement domain verification backup and restore

Hooks up PreferredActivityBackupHelper to the domain verification XML,
replacing the old intent filter verification backup.

Also fixes a leftover bug where linkHandlingAllowed state was not
being deserialized properly.

Bug: 170746586
Bug: 182206123

Test: atest DomainVerificationPackageTest
Test: atest DomainVerificationPersistenceTest

Change-Id: I418c62866da4f82bf387a3b95d0139c2236ea62c