RFR: 8193442: Removing TreeItem from a TreeTableView sometime changes selectedItem

[Jose Pereda]

On Tue, 15 Mar 2022 18:57:50 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> This PR fixes JDK-[8193442](https://bugs.openjdk.java.net/browse/JDK-8193442), but also [JDK-8187596](https://bugs.openjdk.java.net/browse/JDK-8187596), and verifies that the tests mentioned in [JDK-8088157](https://bugs.openjdk.java.net/browse/JDK-8088157) are working (with a minor fix).
>> 
>> When removing an item that is below the selected item from TreeTableView or TreeView controls the selection and/or focus was wrongly changed in some occasions, because a shift in the selection was applied.
>> 
>> This PR adds a method to ControlUtils to get the index of the sibling that is selected/focused or contains the descendant item with the current selection/focus. 
>> 
>> This index is required to compare properly if the selected/focus item is above or below the item that was removed, by comparing the indices of siblings.
>> 
>> Tests have been added to TreeViewTest and TreeTableViewTest based on the existing tests on JDK-8193442 and JDK-8187596. The four tests fail without this PR, pass with it.
>> 
>> In the process, I noticed that the ignored tests referred from JDK-8088157 were already passing, after removing some obsolete asserts, even without this PR.
>
> The GHA test failure on macOS was due to [JDK-8282449](https://bugs.openjdk.java.net/browse/JDK-8282449) and not anything in this PR. I filed a new bug to skip the failing tests until that bug can be fixed. See PR #754.

@kevinrushforth Thanks for the test fix. Do I need to add a change in order to pass the tests again?

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PR: https://git.openjdk.java.net/jfx/pull/753