Filter and header refactoring.

- have AccountFilterUtil to unify account filter implementations.
- modify account header on top of search screens
  Now it is bigger than before (40dip > 32dip), and uses people's
  blue text color instead of gray (issue 5451033)
- introduce ContactListSeparatorTextViewStyle and use it everywhere

Bug: 5269692
Bug: 5451033
Bug: 5429203
Change-Id: Ibe810ff9adaafc74d53b0dcf171a3853f4be039a