Added unit tests for ContentCaptureContext

Test: atest FrameworksCoreTests:android.view.contentcapture.ContentCaptureEventTest \
      FrameworksCoreTests:android.view.contentcapture.ViewNodeTest \
      CtsContentCaptureServiceTestCases
Fixes: 123038898

Change-Id: I0454e14743bb90f3f6883d86fe393efbda09166b
3 files changed