feat: migrate to AWS SDK for Go v2

[kruskall]

AWS released the SDK for Go v2: https://github.com/aws/aws-sdk-go-v2

For a list of features and major improvements, see
https://aws.amazon.com/blogs/developer/aws-sdk-for-go-version-2-general-availability/

The new config loading code will take care of loading values from
default sources, including enrivonment variables (see
https://pkg.go.dev/github.com/aws/aws-sdk-go-v2/config#LoadDefaultConfig).

Modularization is another big improvements that reduces the lambda
extension binary size:

Before: 13M
After: 10M

The secretmanager code was tested by providing a ELASTIC_APM_SECRET_TOKEN using ELASTIC_APM_SECRETS_MANAGER_SECRET_TOKEN_ID and the AWS secret manager (see https://www.elastic.co/guide/en/apm/guide/master/aws-lambda-secrets-manager.html)

AWS also published a migration guide for the SDK for Go v1: https://aws.github.io/aws-sdk-go-v2/docs/migrating/

[apmmachine]

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[AlexanderWert]

@kruskall Thanks for bringing this up.

Actually this replacement should live in the Node.js repo and it's already there:
https://github.com/raw/elastic/apm-agent-nodejs/main/docs/lambda/nodejs-arn-replacement.asciidoc

When looking at the non-released version of the docs (https://www.elastic.co/guide/en/apm/agent/nodejs/master/lambda.html) it's displayed properly.

Also, it's displayed properly for Java: https://www.elastic.co/guide/en/apm/agent/java/current/aws-lambda.html

So potentially it's due to some issues with back-porting / dependencies in the docs?
@bmorelli25 Do you have an idea why it is not resolving for Node.js on current documentation?

[kruskall]

Hey @AlexanderWert 👋 ,

I think you commented on the wrong PR, was this meant for #231?

[AlexanderWert]

@kruskall Ou, sorry, seems I typed in the wrong tab :-D

[simitt]

LGTM!