Cherry-pick #16111 to 7.x: [Metricbeat] Add vpc metricset for aws module

[kaiyan-sheng]

Cherry-pick of PR #16111 to 7.x branch. Original message:

What does this PR do?

This PR is to add support for collecting vpc related monitoring metrics from CloudWatch. This includes AWS/NATGateway, AWS/VPN and AWS/TransitGateway namespaces.

Why is it important?

Users can use this vpc metricset to collect metrics related to their VPCs, for example: bytes received/sent through VPN tunnel, total number of concurrent active TCP connections through NAT gateway, and number of bytes sent/received from transit gateway.

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

Author's Checklist

• generate data.json
• dashboard

How to test this PR locally

Make sure the AWS account you use for testing has VPC related metrics first.
Enable vpc metricset and then change aws.yml to:

- module: aws
  period: 1m
  credential_profile_name: elastic-test
  metricsets:
    - vpc

Related issues

#14854