deps: update metrics to v0.22

[goto-bus-stop]

Update metrics and use the new APIs:

• {increment,decrement}_gauge!() → gauge!().{increment,decrement}
• increment_counter!() → counter!().increment()
• histogram!() → histogram!().record()

[Ptrskay3]

Thanks!
We have pub use metrics actually, so technically it's a minor version upgrade for us too, but I'd like to hold the new release off for a bit. Is that okay for you to use the main branch until then?

[goto-bus-stop]

I'm only using this in a personal side project, so no problem to wait a bit :)

[Ptrskay3]

Just released 0.6.0 that includes this update. Thanks again.