Adding new APIs to UiAutomation.

1. Accessibility service may set a flag to request a compressed
   view of the node tree representing the screen. The compressed
   state does not contain nodes that do to react to user actions
   and do not draw content, i.e. they are dumb view managers. This
   compressed hierarchy was very beneficial to the test team and
   this change is exposing the APIs. The compression has to be
   configurable since old tests are written against uncompressed
   view tree. Basically we do not hide the fact that UIAutomation
   is simply an accessibility service with some other useful APIs.

bug:8051095

2. Accessibility service can perform global actions such as opening
   notifications, opening recent apps, etc. These are also needed
   for UI testing since there is no other way to do it via the
   existing UIAutomation APIs. Basically we do not hide the fact
   that UIAutomation is simply an accessibility service with some
   other useful APIs.

bug:8117582

Change-Id: I7b6e24b5f7a973fdada0cc199cff9f882b10720b