Delete PACKAGE_VERIFIER_USER_CONSENT from Settings.

It isn't used anywhere in the framework, except by incidentd - that
usage is also removed.

Any such setting is private to the verifier and not the business of
the framework.

Test: atest SettingsProviderTest
Test: Still builds
Bug: 135751498
Change-Id: Ia6424d8ce811560e4ba72ada003dc08475d5123e