RFR: 8321300: Cleanup TestHFA

[Martin Doerr]

On Mon, 4 Dec 2023 21:25:41 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> I'd like to clean this up: Use the canonical layouts which are available in JDK22. Use try-with-resources for `Arena.ofConfined()`.

Thanks for the reviews! The Pre-submit test errors are unrelated.

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PR Comment: https://git.openjdk.org/jdk/pull/16959#issuecomment-1840440238