Update strings and layout for enterprise privacy

This CL continues the finalization of UI layout and strings for the
enterprise privacy page:
* Turn footer into a header
* Update strings
* Dynamically generate summaries for entry points in security page

Bug: 32692748
Test: m RunSettingsRoboTests

Change-Id: Ibf248ac269380fb1b919b01f88f721130060b7f9
15 files changed