Introduce boolean flags to show/hide items in Security & location.

This adds 6 new boolean flags:
config_show_manage_device_admin
config_show_unlock_set_or_change
config_show_screen_pinning_settings
config_show_manage_trust_agents
config_show_show_password
config_show_trust_agent_click_intent

Which when individually set to false, will hide the item from "Security
& location". It will also hide them from surfacing in search results.

Bug:62379222
Test: make RunSettingsRoboTests
ROBOTEST_FILTER=com.android.settings.security
Change-Id: I58d82cbc7f366a9666cdb0f7cd1b90ebbaf418f4

src/com/android/settings/security/ChangeScreenLockPreferenceController.java

@@ -67,7 +67,7 @@ public class ChangeScreenLockPreferenceController extends AbstractPreferenceCont
 
     @Override
     public boolean isAvailable() {
-        return true;
+        return mContext.getResources().getBoolean(R.bool.config_show_unlock_set_or_change);
     }
 
     @Override