RFR: 8354078: Shenandoah: Make the generational mode be non-experimental (implementation)

[Roman Kennke]

On Fri, 16 May 2025 17:30:11 GMT, William Kemper <wkemper at openjdk.org> wrote:

> Testing:
> 
> % ./build/linux-x86_64-server-fastdebug/jdk/bin/java -XX:+UseShenandoahGC -XX:ShenandoahGCMode=generational --version
> openjdk 25 2025-09-16
> OpenJDK Runtime Environment (fastdebug build 25-make-genshen-non-experimental)
> OpenJDK 64-Bit Server VM (fastdebug build 25-make-genshen-non-experimental, mixed mode)

Many tests specify `-XX:+UseExperimentalVMOptions` to be able to use generational mode. Those `-XX:+UseExperimentalVMOptions` should be removed.

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PR Comment: https://git.openjdk.org/jdk/pull/25270#issuecomment-2891447874