RFR: 8277397: ZGC: Add JFR event for temporary latency measurements

[Erik Österlund]

On Thu, 18 Nov 2021 13:09:59 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.

Looks good.

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Marked as reviewed by eosterlund (Reviewer).

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