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

[Marius Hanl]

On Mon, 7 Nov 2022 20:13:18 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> 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).
>
> could you please create an umbrella ticket listing all the types that need to be added to the test and/or fixed?
> 
> here is an example of such ticket (with an umbrella unicode):
> [JDK-8241364](https://bugs.openjdk.org/browse/JDK-8241364)

created https://bugs.openjdk.org/browse/JDK-8296609

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