RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v17]

[Johannes Bechberger]

On Tue, 27 May 2025 16:34:14 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

>> It seems to normally be a pointer. I'll try the forward declaration later.
>
> Don't worry if it's too hard. It would just be a nice thing to eliminate these special includes from the header file.

The signal.h is apparently included in the `globaldefinitions_gcc`, so no need to include it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2111351553