Add skipBlock option to improve performance with event handlers

[stwiname]

Description

If a project only has event handlers there is not always a need to fetch all the block content. This can lead to ~10% performance increase in indexing speed.

skipBlock can be set in node runner options or in cli flags. It will automatically disable this if handlers other than event handlers are found.

I also found a bug where node runner options in project.yaml were broken because of default values in yargs. This will need to be fixed in other SDKs

Completes #1889 for Substrate

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update Document node runner options, specifically skipTransactions documentation#400

Checklist

• I have tested locally
• I have performed a self review of my changes
• Updated any relevant documentation Document node runner options, specifically skipTransactions documentation#400
• Linked to any relevant issues
• I have added tests relevant to my changes
• Any dependent changes have been merged and published in downstream modules
• My code is up to date with the base branch
• I have updated relevant changelogs. We suggest using chan

[jiqiang90]

We could define event only handler in this way, but we could face another issue, we could not know whether user try to access block content from event which we have wrapped previously.

const wrappedEvents = wrapEvents(wrappedExtrinsics, events, wrappedBlock);

We can test this scenarios with starter, and we found error was thrown, but not clearly enough, could be very difficult to debug.

https://github.com/subquery/subql-starter/blob/96b09b6aa3a0c6506c423acf628f117cd47e9f83/Polkadot/Polkadot-starter/src/mappings/mappingHandlers.ts#L41

I think we could implement within wrapped event, if block content is accessed in handler, we could provide more friendly warning/error. Or even refetch the block content.

[stwiname]

This is why there is the skipBlock option, users have to opt into it and test it themselves. They should update their handler types accordingly