Proposed commit message

This is a follow-up to #41188 where I am adding support to source linked accounts when using log_group_name_prefix to derive log groups.

PR introduce include_linked_accounts_for_prefix_mode boolean property, which is disabled by default. If enabled (include_linked_accounts_for_prefix_mode : true), then we set includeLinkedAccounts property of the DescribeLogGroups API [1] to obtain log groups matching prefix and included in linked accounts of the monitoring account.

ex:-

- type: aws-cloudwatch
  ...
  log_group_name_prefix : /development/AppA/
  include_linked_accounts_for_prefix_mode: true
  ... 

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

This require a linked cloudwatch account. If already has one, then,

• Push logs to a newly created log group OR use an already existing log group in a source account
  • Note - you may use data-gen Go program to generate and push logs to your log group (using output CLOUDWATCH_LOG) [2]
• Configure filebeat cloudwatch input with log_group_name_prefix with desired prefix & set include_linked_accounts_for_prefix_mode to value true (enabled)
• Run filebeat and observe logs in Kibana discover which include logs from log groups (that match provided prefix)

Related issues

• Closes [Filebeat] [AWS] Support getting cloudwatch logs from linked cross-account monitoring source accounts  #36642

[1] - https://docs.aws.amazon.com/AmazonCloudWatchLogs/latest/APIReference/API_DescribeLogGroups.html
[2] - https://github.com/Kavindu-Dodan/data-gen