Cherry-pick #26832 to 7.x: Add Proxy settings to AWS Common

[kaiyan-sheng]

Cherry-pick of PR #26832 to 7.x branch. Original message:

What does this PR do?

Adds the ability to set a proxy to the AWS SDK config.

Why is it important?

This is useful when the Beats outbound connections need to go through a proxy but don't want it to affect other inputs/outputs. When using the HTTP_PROXY env variable, this also affects the Beats output to Elasticsearch. Having a dedicated setting allows only the AWS requests to be proxied and not affect any other input/output.

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.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

Use cases

Screenshots

Logs

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)