PreferenceActivity Fragment security

Provides a way for PreferenceActivities to verify that they
aren't being launched with Fragments not meant to be attached to
them. Default implementation will fail verification for apps built
with KLP. This will not affect apps built for earlier targets.

Also, make sure that the class being instantiated is a Fragment and
not some random class.

Bug: 9901133

Change-Id: I564cd5168eabcadd7594ea8011e2081ebebfe063