RFR: 8277397: ZGC: Add JFR event for temporary latency measurements [v2]

[Stefan Karlsson]

On Fri, 19 Nov 2021 08:02:12 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> I often measure latencies and stalls using JFR events. I'd like to add an event that can be used for these ad-hoc measurements during development and debugging.
>
> Stefan Karlsson has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review jbachorik

I discussed the naming of this event with @pliden, and we decided to rename it to make it more clear that this was only intended for debugging/development of ZGC.

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PR: https://git.openjdk.java.net/jdk/pull/6454