New feature “Text and reading options” for SetupWizard, Wallpaper, and Settings (6/n).

- Create new preview preference.
1) It will be integrated with TextReadingPreferenceFragment, and sub
previews layouts like app launchers, conversation messages, and mail
content.

Bug: 211503117
Test: make -j64 RunSettingsRoboTests ROBOTEST_FILTER=TextReadingPreviewPreferenceTest
Change-Id: I2d82d58438ee3f96c5a8dbb1809a0d6bdf3a00a2