RFR: 8296330: Tests: Add layout container snapping tests [v2]

[Marius Hanl]

On Mon, 7 Nov 2022 19:46:41 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> Marius Hanl has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   8296330: Added javadoc, made delta a constant, reordered working container on top and renamed ContainerInstruction to ContainerCreator
>
> modules/javafx.graphics/src/test/java/test/javafx/scene/layout/SnappingTest.java line 155:
> 
>> 153: //                new ContainerCreator<>(StackPane::new),
>> 154: //                new ContainerCreator<>(BorderPane::new),
>> 155: //                new ContainerCreator<>(node -> {
> 
> 1. should we create corresponding bug reports for the commented out containers?
> 2. should we also test other descendants of Pane (am I correct in guessing it's a Pane you call "container")?

1. Yes. We may want to create something like an 'epic'. I see that in the past it was called an 'umbrella issue'
2. Yeah we should, but the goal of this PR is to test all layout container, specified in `javafx.scene.layout`.

Other nodes needs more special test cases, e.g. can't be solved in a generic test. `Control` nodes are also mostly fine since the `layoutChildren` method in the `SkinBase` will receive the already snapped insets (so it is harder to do the wrong thing).

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PR: https://git.openjdk.org/jfx/pull/936