RFR: 8037914: Add JFR event for string deduplication

[Erik Gahlin]

On Tue, 28 Oct 2025 10:09:58 GMT, Francesco Andreuzzi <fandreuzzi at openjdk.org> wrote:

> In this PR I introduce two new JFR events:
> - `jdk.StringDeduplicationStatistics`
> - `jdk.StringDeduplicationTimes`
> 
> The events are emitted every time a deduplication cycle happens, and they contain information about that cycle only.
> 
> Passes tier1 and tier2 (fastdebug).

Why do you need two events instead of one?

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PR Comment: https://git.openjdk.org/jdk/pull/28015#issuecomment-3458838597