Simplified View.onProvideContentCaptureStructure()

That method was returning a boolean to indicate whether the IntelligenceManager
should be notify, so views with virtual hierarchy could return false.

But now it returns void and always notify, which makes the API easier to
understand and use.

Bug: 117944706

Test: m -j update-api doc-comment-check-docs
Test: atest CtsAutoFillServiceTestCases

Change-Id: I216cacb6edb144239b6eabe56ab177fc2582e1aa