node: update callback function API

[silesky]

Pass callback as second argument with (err, result) signature, to both make consistent with legacy analytics-node and because it's quite idiomatic.

 ajs.track(
        {
          anonymousId: 'bar',
          event: 'event name',
        },
        (err, ctx) => {
          if (err) {
            // do something with error
           }
        }
      )

[changeset-bot]

🦋 Changeset detected

Latest commit: 196d30f

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

This PR includes changesets to release 3 packages

Name	Type
@segment/analytics-core	Patch
@segment/analytics-next	Patch
@segment/analytics-node	Patch

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