Add RootTargetPreparer for explicitly specifying the root dependency

Before, the test gets root implicitly via DeviceSetup which
wasn't intented.

Test: presubmit
Bug: 325094408
Bug: 331876076
(cherry picked from https://android-review.googlesource.com/q/commit:7c829f1edc40cef981e3e3837ffd9f4a7b6f3113)
Merged-In: I9b34a85025a6aa4f138483202fd11db0cbb8b04b
Change-Id: I9b34a85025a6aa4f138483202fd11db0cbb8b04b
(cherry picked from commit 3c4f5273)