RFR: 8349373: Support JavaFX preview features [v6]

[Andy Goryachev]

On Sat, 15 Mar 2025 03:41:29 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> This PR contains a definition of preview features for JavaFX, as well as a helper class to verify that an application has opted into preview features.
>
> Michael Strauß has updated the pull request incrementally with one additional commit since the last revision:
> 
>   banner -> warning

Marked as reviewed by angorya (Reviewer).

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PR Review: https://git.openjdk.org/jfx/pull/1359#pullrequestreview-2690745635