First pass on consolidating usage of AccountManager (1/2)

* Move AccountUtil.getDefaultGoogleAccount to AccountTypeManager

Bug: 31776692

Test:
  - manual: turn on Search__yenta flag and see if we can get default
    Google account
  - unit tests all passed

Change-Id: I068a44b0870867cec6dd4ff240e0006df8b8f24d