Feature flag to disable head update on attestation basis

[terencechain]

Computing head for every new attestation is a nice to have but may be too excessive, we can change the strategy to updating head every second. Opening this as an option to not compute head on every attestation.
Another option is to remove the tracing for the following methods. They seem to be the main bottlenecks.

[codecov]

Codecov Report

Merging #4802 into master will not change coverage by %.
The diff coverage is n/a.

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[prestonvanloon]

Can you add it as a feature flag? Like we have --disable-strict-attestation-pubsub-verification which gives us the option to disable this in an emergency.

[terencechain]

Can you add it as a feature flag? Like we have --disable-strict-attestation-pubsub-verification which gives us the option to disable this in an emergency.

this is a good idea, I'm leaning towards default behavior is compute head on per attestation, the feature flag will disable that.

It's generally good for the node to get head updated as frequently incoming attestation if there's not much penalties to go with it