feat: implement `gauge` metrics for key feature flags

[0x416e746f6e]

it would be good for monitoring purposes for op-rbuilder to export gauge (values 0 or 1) metrics for when this or that particular feature flag is enabled or not. for example:

• feat_revert_protection => 1 when --builder.enable-revert-protection is in force, 0 otherwise
• feat_flashblocks => 1 when --flashblocks.enabled is in force, 0 otherwise
• feat_flashtestations => 1 for --flashtestations.enabled, 0 otherwise
• and so on...

[akundaz]

These should not be reported as metrics, it adds too much overhead if we need to add a metric and corresponding chart for every flag.

Instead, flag settings should be checked into git and current deployments should match the values in the repo.

[0x416e746f6e]

flag settings should be checked into git and current deployments should match the values in the repo

that's not possible in general case

[akundaz]

Can you be more specific? This is a pretty standard practice. The only caveat I can think of is for secrets which are managed separately