Checklist

• My issue is specific & actionable.
• I am not suggesting a protocol enhancement.
• I have searched on the issue tracker for my issue.

Description

When initializing a new instance, enabling datastore metrics should be optional. If not specified, the default should be to have metrics off. Metrics should be off by default as they have a minor performance impact and result in a more complex config.

• New -metrics boolean flag to ipfs init command.
• Default config does not configure a measure datastore for any datastore.
• Existings configs will not be changed.

If -measure=true is specified during ipfs init then the datastore config will be as it is today, with each datastore having a parent measure type of datastore in its spec config.

If -measure=false is specified or the flag is not provided during ipfs init then each datastore in the datastore config will not have parent measure type of datastore, and instead just the datastore will be configured with no child in its spec config.