[8.17](backport #41834) [filebeat][gcs] - Refactor & cleanup with updates to some default values and docs

[mergify]

Type of change

• Cleanup
• Docs

Proposed commit message

This PR is a successor to an older closed PR. The older PR has been split into two parts, this being the one containing the necessary refactor and updates to default values and docs.

Default values have been updated to be more in line with standard mode of operations.

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.

Disruptive User Impact

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Relates [Meta][GCS] - Improvements and addition of new features to the GCS input #41107
• Superseds [filebeat][gcs] - Added retry config & refactored the default config options #41699

Use cases

Screenshots

Logs

---

This is an automatic backport of pull request #41834 done by [Mergify](https://mergify.com).

[botelastic]

This pull request doesn't have a Team:<team> label.

[ShourieG]

/test