RFR: 8334137: Marlin: replace sun.misc.Unsafe memory access methods with FFM [v8]

[Kevin Rushforth]

On Wed, 11 Jun 2025 19:40:09 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> It doesn't really matter, but personally I try to use the built in functionality.
>
> ~~I decided to fix the constructor now (simple cleanup without any behavior change).~~

I removed the explicit check.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1814#discussion_r2140935641