Migrate LegalSettings to DashboardFragment

- CopyrightPreferenceController
- LegalPreferenceController
- LicensePreferenceController
- TermsPreferenceController
- WallpaperAttributionsPreferenceController
- WebViewLicensePreferenceController

Test: manual
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.deviceinfo
      make RunSettingsRoboTests -j ROBOTEST_FILTER=CodeInspectionTest
      atest UniquePreferenceTest

Change-Id: I28108eb926f9efec63390c2354cb0ebc0a785ec2