Follow AWS Lambda handler resolution for nodejs.

[ianmuninio]

This PR will follow how AWS Lambda resolves their handler. I will create another PR in newrelic/newrelic-lambda-extension to address the logging issue that the extension is sending to newrelic logs console.

Edit 1:
PR for lambda extension for nodejs newrelic/newrelic-lambda-extension#190

lambda.cjs
export default { handler: () => 'hello world' }

AWS: lambda.default.handler //-> passed
NewRelic: lambda.default.handler //-> failed

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