Initial integration test for BugReportReceiver.

These tests rely in the UI Automator to interact with the UI and
follow the workflow below:

 * creates the bug report files
 * generates the BUGREPORT_FINISHED intent
 * emulate user actions to share the intent with a custom activity
 * asserts the extras received by the custom activity

It still have some limitations, like requiring the phone to be unlocked
and having the bugreport warning already checked, and those will be
addressed in future CLs.

BUG: 25752530
Change-Id: I01d7fad9f94daf156b728cbb9ef228bbfa6ee0f5