update Lambda instrumentation docs to mention the Node.js APM agent layer #2615
Description
https://www.elastic.co/guide/en/apm/guide/master/aws-lambda-extension.html#aws-lambda-handler was updated to describe using the Node.js APM agent lambda layer (in elastic/apm-aws-lambda#139). However, the Node.js APM agent-specific lambda doc page (https://www.elastic.co/guide/en/apm/agent/nodejs/current/lambda.html) doesn't mention installing the layer.
From some recent discussion, @AlexanderWert and I were going to revisit these two doc pages. Some notes/plans:
- Move most of the content for setting up a Lambda to the language-specific pages.
- Perhaps renaming the general extension page to be about "Elastic APM and Lambda" and no specifically about the extension, which is an implementation detail.
- See if the language-specific getting started steps can be made a bit clearer.
This issue about the Node.js APM agent docs parts of that.