RFR: 8292265: Add old gen used field at G1HeapSummary JFR event. [v2]

[Sangheon Kim]

On Wed, 30 Nov 2022 09:21:15 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Sangheon Kim has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Thomas review
>
> Lgtm.

Thanks @tschatzl and @albertnetymk for your reviews.

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PR: https://git.openjdk.org/jdk/pull/11303