Emit command latency events using JFR

[HashJang]

Fix: #1820

On the basis of current JFR Event generation, add JFR event for CommandLatencyEvent. And support summary report through JMC like the graph below:

[sokomishalov]

LGTM

[mp911de]

I'm not sure that's something we want. Introducing JFR support for metrics events can impose a lot of load in default configurations. I think we need to document that in the reference docs and emphasize on how to disable JFR metrics events.

[HashJang]

metrics

I'm not sure that's something we want. Introducing JFR support for metrics events can impose a lot of load in default configurations. I think we need to document that in the reference docs and emphasize on how to disable JFR metrics events.

JFR Event for Command Latency is only produced when Command Latency Event is created and Command Latency Event is created at scheduled rates. The amount would not be much enough to cause performance decrease.

And this JFR Event will only be created when:

1. Command Latency Event is enabled;
2. JFR Records is enabled
3. the event is not disabled in JFR event configuration.

[mp911de]

Thank you for your contribution. That's merged and polished now.