all: add force option for metric system

[rjl493456442]

fix #17601

[nonsense]

@rjl493456442 could you please add a short summary on why this is necessary?

I understand that this is needed because you want to record hashrate even if the Metrics system is not enabled - why is this necessary?

I am sure this has been discussed already, but please help me understand as well :)

[rjl493456442]

@nonsense, To be honest, there is no discussion whether should we record the hashrate even the system is enable or not.

Currently, our metrics system has a global switch to control all metric instances, but sometimes we not only use metrics library to record some system detail information but also record some necessary information(e.g. local hashrate if you are mining).

This PR just wants to make our metrics system more flexible. Because the metrcis library allows us to easily record and calculate some necessary system information. May be in the future we need to record some other necessary data in the runtime, so this PR will be helpful :)

Do you think it make sense?

[nonsense]

@rjl493456442 sure, it makes sense. I don't have strong feelings about it, so if you find this helpful, I approve.

[karalabe]

Would't it make more sense to add a new set of methods instead?

E.g. Instead of func NewRegisteredCounter(name string, r Registry, force bool) Counter we would have the original func NewRegisteredCounter(name string, r Registry) Counter and an additional new func NewRegisteredCounterForced(name string, r Registry) Counter?

This way we would retain the original API, would not introduce a big refactor all over the codebase and future metrics would remain clean as they are now. We'd only need to explicitly tag a couple metrics that are always needed.

[rjl493456442]

@karalabe I just explicitly tag the meter in order to achieve a minimum range of modifications.

There are many different types of metrics(Counter, Timer,Gauge, etc), and more complicated is some metrics relays on other metrics. I don't want to make the metrics too complicated so only meter is tagged.

[karalabe]

Don't we need Forced here?

[karalabe]

LGTM