Add an @hide way to adjust CursorAnchorInfo for another Matrix

This is a preparation to support CursorAnchorInfo API in ActivityView.

In order to enable the system to automatically adjust CursorAnchorInfo
object between the IME client and IME, there needs to be an @hide
method to create a new CursorAnchorInfo instance with applying an
additional coordinate transformation Matrix, which is what this CL
does.

This CL also cleans up CursorAnchorInfoTest.java as most of test there
were already moved to CTS [1].

Anyway, this is a mechanical change.  There should be no behavior
change in existing methods in CursorAnchorInfo.

 [1]: Ib758bddff34b4722b39c94e7ad4e8f8da2bb8b92
      c4ef1d6ec22dc2af2ed339fd4e78075903783be0

Bug: 115693908
Test: atest CtsInputMethodTestCases:CursorAnchorInfoTest
Test: atest FrameworksCoreTests:CursorAnchorInfoTest
Change-Id: Ic7f9057623ffc61ec7a6121735dc39adecf4649d