Remove CursorAnchorInfo#createForAdditionalParentMatrix()

This CL logically reverts my previous CL [1], which added an @hide
method

  CursorAnchorInfo#createForAdditionalParentMatrix()

as a preparation to support CursorAnchorInfo API on ActivityView.

Now that InputMethodManager#reportActivityView() is removed [2], we
also do not need this @hide method any more too.

Note also that CursorAnchorInfo is now fully tested in CTS rather than
FrameworksCoreTests [3].  Thus it's fine with removing
CursorAnchorInfoTest.java from FrameworksCoreTests.

  [1]: Ic7f9057623ffc61ec7a6121735dc39adecf4649d
       e4410a13
  [2]: Idd60d96a39f827197d189beb5de016446576d9cd
       44c499d8
  [3]: Ib758bddff34b4722b39c94e7ad4e8f8da2bb8b92
       c4ef1d6ec22dc2af2ed339fd4e78075903783be0

Bug: 115693908
Bug: 179161778
Test: atest CtsInputMethodTestCases:CursorAnchorInfoTest
Change-Id: I0a05453eeed863db5bfe4b965ab4bcbad67f2783