fix(l2geth): add an env var METRICS_ENABLE for MetricsEnabledFlag

[timmyers]

Description
Adds an env var METRICS_ENABLE for the MetricsEnabledFlag CLI arg.

[changeset-bot]

🦋 Changeset detected

Latest commit: 0ce4cc8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@eth-optimism/l2geth	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[tynes]

Thanks for the PR @timmyers! Will merge this. Wondering your thoughts on using environment variables vs CLI flags for configuration - we are considering the removal of env var based configuration when we migrate to using the latest version of go-ethereum as to reduce the diff as much as possible

[timmyers]

I prefer env vars, I find them to be the cleanest, especially when defining (kubernetes) manifests as code.
It would be great if we could make some effort to upstream env var support into geth.

[tynes]

I prefer env vars, I find them to be the cleanest, especially when defining (kubernetes) manifests as code.
It would be great if we could make some effort to upstream env var support into geth.

This has been suggested upstream before ethereum/go-ethereum#14346

[timmyers]

Ah I see. Well CLI args are definitely workable if at some point you want to remove them to slim the diff. The config file option is by far the worst to work with for me.