Fixing bugs exposed when moving accessibility CTS tests to UiAutomation.

1. UiAutomation#executeAndWaitForEvent method was invoking the passed
   runnable while holding the lock which may lead to a deadlock. For
   example: a runnable that calls getActivity() gets us into a state
   like this.

2. UI automation services did not get all capabilities such a
   service can have. Now a UI test service gets all of them.

3. When UiAutomation was exiting for event fired as a result of a
   performed action, it was checking whether the received evnet time
   is strictly before the time of executing the command that should
   fire the event. However, if the execution is fast enough, i.e.
   less than one millisecond, then the event time and the execution
   time are the same. This was leading to a missed signal in rare
   cases.

4. AccessibilityNodeInfoCache was not clearing the relevant state
   for accessibility focus clearing event.

5. Accessibility text traversal in TextView was partially using text
   and partially content description - broken. Now we are using the
   text since for text view and content desc for other views. In other
   words, we are using the most precise text we have.

6. AccessibilityManagerService was not granting capabilities of a
   UiAutomation service - plainly wrong.

CTS change:https://googleplex-android-review.googlesource.com/#/c/300693/

bug:8695422
bug:8657560

Change-Id: I9afc5c3c69eb51f1c01930959232f44681b15e86