Make KafkaMetrics refresh interval configurable

[jonatan-ivanov]

See #6206

[jonatan-ivanov]

@spryslmatej I removed a few ctors to make the changes smaller (we should not support all the possible combinations or all the parameters). Could you please check if this is usable for you?

[shakuzen]

I wonder if we couldn't use the MeterRegistry's step by default if a refresh interval isn't provided. We could only do that for PushMeterRegistry with PushRegistryConfig, but it might alleviate some need to pass a custom refresh interval.

[jonatan-ivanov]

I like this idea, I assume you were also thinking about getting the step in bindTo from the registry and not letting the user pass the config to a ctor of KafkaMetrics.

I tried to implement it but I realized that our registries do not return their config objects.
MeterRegistry does not have a reference to MeterRegistryConfig and registries don't pass their config "up" to it by calling a super ctor (there is none they could call).

I'm not sure we can "fix" this on the MeterRegistry level but we can add a getter to PushMeterRegistry. The problem with that is since registries don't know their config type, we either return PushRegistryConfig everywhere (e.g. in StepMeterRegistry and in every other implementations) or do something like this:

public <T extends PushRegistryConfig> T getConfig() {
    return (T) config;
}

Let's discuss this internally and see what we can do.

[jonatan-ivanov]

I created #6342, in the meantime, we can go with the refresh interval parameter in this PR.

[jonatan-ivanov]

@spryslmatej A new SNAPSHOT release should be created in the next few minutes, could you please check if it works for you?

[spryslmatej]

@jonatan-ivanov Tested with version 1.16.0-SNAPSHOT, works as expected 👍

Thank you very much!