RFR: 8350048: Enforce threading restrictions for show and hide methods in Window, Control, and Skin [v3]

[Andy Goryachev]

On Thu, 27 Feb 2025 15:57:07 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> - enforced fx application thread
>> - clarify doc where an `IllegalStateException` can get thrown, such as hide() and show()
>> - clarified `ComboBoxBase::show`
>> - added a headful test `TestThreadingRestrictions`
>
> Andy Goryachev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review comments

created CSR https://bugs.openjdk.org/browse/JDK-8350962

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PR Comment: https://git.openjdk.org/jfx/pull/1717#issuecomment-2691039623