Use regular preference theme for setup wizard

Use the regular preference theme rather than the settings specific
one, because setup wizard doesn't want the space reserved for icon
done in the settings theme.

Also minor changes to Espresso FirstIdViewMatcher for a more
descriptive message.

Test: runtest --path tests/app/src/com/android/settings/dashboard/PreferenceThemeTest.java
Bug: 33922083
Change-Id: Ic878ccf7b01cfa090ca4587b160e1f9dedfb8d3a