Metrics not getting enabled by default

[rkuris]

Describe the bug
No firewood metrics are being reported to prometheus in the latest version of avalanchego/firewood combo.

To Reproduce
Spin up a bootstrap test, the metrics aren't making it to grafana

Expected behavior
I expected the firewood metrics would be enabled.

Possible Solutions
This is likely a problem on the coreth side as the metrics initialization has moved.

[rkuris]

It seems that StartMetrics is only called when expensive metrics are enabled. I think this may have changed as previously the metrics were initialized on all re-execution tests.

[rkuris]

It seems that enabling expensive metrics is still not enough to get metrics reported through our local grafana instance.

[rkuris]

Likely related to side effects from #4418

[rkuris]

There's a rumor that collected metrics from firewood are prefixed as well. If it's true, we need to figure this out and remove any prefixes added by avalanchego.