Misc fix on settings themes.

- Use dark status bar for confirmDeviceCreditials theme to match dark
  window background
- Remove SubSettingsDialogWhenLarge theme in favor of full screen
  settings for O.
- Update font/dize preview text color to match light background

Bug: 33558692
Test: visual

Change-Id: Id8704c96e2ce35247e80e50eefd531786479b193