Cherry-pick of PR #23539 to 7.x branch. Original message:

What does this PR do?

This PR is to deprecate aws_partition config parameter and use endpoint with regions instead in order to make the AWS configuration less confusing.

Why is it important?

There is overlap between aws_partition and endpoint. We decide to use endpoint moving forward.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

How to test this PR locally

1. Test case with no endpoint specified
   Enable aws module:

./metricbeat modules enable aws

Change aws.yml config file to run ec2 metricset:

- module: aws
  period: 5m
  credential_profile_name: elastic-beats
  metricsets:
    - ec2

This should work like it used to.

2. Test case with endpoint

- module: aws
  period: 5m
  credential_profile_name: elastic-beats
  endpoint: amazonaws.com
  regions: us-east-1
  metricsets:
    - ec2

Start Metricbeat and ec2 metricset should work and collect metrics for instances in us-east-1.

Related issues

Closes #23153