RFR: 8356690: Update JUnit to 5.12.2

[Kevin Rushforth]

On Sat, 10 May 2025 23:41:44 GMT, Marius Hanl <mhanl at openjdk.org> wrote:

> This PR bumps the JUnit version to 5.12.2.
> Also removed 2 now unused variables since I phased out the JUnit Vintage Engine + Hamcrest.
> 
> Changelog: https://junit.org/junit5/docs/current/release-notes/index.html#release-notes-5.12.2
> The mentioned deprecations do not affect us.
> 
> Interesting new features:
> - Thread dumps on test timeouts
> - Parameterized test validation improvements
> - JRE-based conditions such as @EnabledOnJre and @DisabledForJreRange now support arbitrary Java versions

@arapte can you be the second reviewer?

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PR Comment: https://git.openjdk.org/jfx/pull/1803#issuecomment-2890734243