[jdk17u] RFR: 8274560: JFR: Add test for OldObjectSample event when using Shenandoah

[Aleksey Shipilev]

On Fri, 12 Nov 2021 08:46:47 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Clean backport to improve Shenandoah testing.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug `jdk/jfr/event/oldobject` passes

Got the push approval.

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PR: https://git.openjdk.java.net/jdk17u/pull/255